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Aeronautical 

Annual. 


EDITED  BY  JAMES  MEANS. 

PRICE  ONE  DOLLAR. 

BY  MAIL  POSTPAID  TO  ANY  ADDRESS  IN  THE  POSTAL  UNION 

$1.12 


THE  ORIGINAL  NUMBERS  OF  ThE  AERONAUTICAL  AnTWAL 
WERE  PUBLISHED  IN  1895,  1896  AND  1897. 

THIS  EPITOME  IS  PUBLISHED  IN  THE  YEAR 

1910. 


BOSTON,  MASS.,  U.  S.  A. 

W.  B.  CLARKE  COMPANY, 

26  Tremont  St. 


Copyright  1895,  ^^96,  1S97  *9*0f 

By  JAMES  MEAN'S. 

International  Copyright  Secured. 


(Th?  IBnfkhipU  attb  d^urrliiU 


2TZ  E 


TO  THE  STUDENTS 

OF 


AVIATION 


I . 

t, 


INTRODUCTION. 


The  three  numbers  of  The  Aeronautical  Annual  men- 
tioned on  the  title-page  being  now  out  of  print,  the  editor  has 
selected  several  of  the  most  important  articles  and  reprinted 
them  here. 

This  compilation  has  for  its  primary  object  the  encourage- 
ment of  those  who  are  just  beginning  the  study  of  aviation. 

In  the  effort  to  reach  a good  understanding  of  the  achieve- 
ments of  to-day  the  student  may  do  well  to  learn  of  the  work 
of  the  pathfinders. 


May,  1910. 


A 


CONTENTS 


Page 

I.  Practical  Experiments  for  the  Development  of  Human 

Flight 7 

By  Otto  Lilienthal. 

II.  Wheeling  and  Flying  . 21 

By  the  Editor. 

III.  Our  Teachers  in  Sailing  Flight 24 

By  Otto  Lilienthal. 

IV.  At  Rhinow 32 

By  Otto  Lilienthal. 

V.  The  Best  Shapes  for  Wings 35 

By  Otto  Lilienthal. 

VI.  Otto  Lilienthal.  A Memorial  Address  ....  39 

By  Karl  Miillenhoff. 

VII.  Octave  Chanute 48 

VIII.  Recent  Experiments  in  Gliding  Flight  ....  52 

By  Octave  Chanute. 

IX.  Soaring  Flight 76 

By  Octave  Chanute. 

X.  Darwin’s  Observations 83 

XI.  How  A Bird  Soars 85 

By  Professor  William  H.  Pickering. 

XII.  Natural  and  Artificial  Flight 88 

By  Sir  Hiram  S.  Maxim. 

XIII.  Speed  Table 118 

XIV.  Gliding  Experiments 118 

By  Percy  S.  Pilcher. 

XV.  Wise  upon  Henson 121 

XVI.  Table  of  Wind  Velocities 124 

XVII.  Story  of  Experiments  in  Mechanical  Flight  . . . 125 

By  Samuel  Pierpont  Langley. 

XVIII.  The  Aerodromes  in  Flight 140 

By  Alexander  GraTiara  Bell. 

XIX.  The  Scientific  Value  of  Flying  Models  ....  143 

By  the  Editor. 

XX.  Abbott  Lawrence  Rotch  -149 

XXL  The  Relation  of  the  Wind  to  Aerial  Navigation  , . 150 

By  Professor  Abbott  Lawrence  Rotch. 

XXII.  On  Aerial  Navigation.  Part  1 156 

By  Sir  George  Cayley,  Bart.  Written  in  1809. 

XXIII.  The  same.  Part  II 168 

XXIV.  Aerial  Locomotion  . . 176 

By  F.  H.  Wenham  . 

XXV.  The  Blue  Hill  Meteorological  Observatory  . . . 208 

XXVI.  Miscellany,  1897 210 

XXVII.  Miscellany,  1910 213 

XXVIII.  Editorial 218 


LIST  OF  PLATES, 


I.  Lilienthal’s  Air  Sailer  in  1895  ....  Frontispiece 

II.  Lilienthal  Machine.  Autograph  Letter  . . To  face  page  12 

III.  Gliding 16 

IV.  Gliding 18 

V.  The  Conical  Hill 20 

VI.  The  Development  of  the  Wheel  ......  22 

VII.  Portrait  of  Otto  Lilienthal 40 

VIII.  Portrait  of  Octave  Chanute 48 

IX.  Chanute’s  Gliders 54 

X.  Chanute’s  Multiple  Surface  Glide.r 58 

XL  Chanute’s  Gliders  60 

XII.  Scale  Drawing  of  Glider 62 

XIII.  Gliders 64 

XIV.  Camp  Chanute.  Blue  Hill  Observatory  ....  74 

XV.  Maxim’s  Apparatus 104 

XVI.  Henson’s  New  Aerial  Steam  Carriage 122 

XVII.  Langley’s  Aerodrome.  Contours  of  Albatross  and  Vulture  126 

XVIII.  Portrait  of  Abbott  Lawrence  Rotch 150 


LILIENTHAL. 


Born,  1848;  Died,  1896. 


The  epoch-making  work  of  Otto  Lilienthal  gave  ocular 
demonstration  of  two  facts  which  before  his  time  had 
been  generally  disbelieved. 

First : That  it  is  possible  for  a man,  in  free  flight,  using 

extended  surfaces  of  moderate  dimensions,  to  derive  support 
from  the  impact  of  the  air  upon  those  surfaces  without  the  aid 
of  the  buoyant  power  of  a gas  lighter  than  air. 

Second  : That  it  is  possible  for  a man,  in  free  flight,  to  acquire 

a fair  degree  of  control  of  an  aeroplane  apparatus. 


[From  Aero.  Ann.,  1896.] 


PRACTICAL  EXPERIMENTS  FOR  THE  DEVELOP- 
MENT OF  HUMAN  FLIGHT. 

By  Otto  Lilienthal. 


( Written  expressly  for  the  Annual.) 


Whoever  has  followed  with  attention  the  technical  treatises 
on  flying  will  have  become  convinced  that  human  flight  cannot 
be  brought  about  by  one  single  invention,  but  is  proceeding 
towards  its  perfection  by  a gradual  development;  for  only 
those  trials  have  met  with  success  which  correspond  with  such 
a development. 

Formerly  men  sought  to  construct  flying  machines  in  a 
complete  form,  at  once  capable  of  solving  the  problem,  but 
gradually  the  conviction  came  that  our  physical  and  technical 
knowledge  and  our  practical  experiences  were  by  far  insuffl- 
cient  to  overcome  a mechanical  task  of  such  magnitude  with- 
out more  preliminaries. 

Those  proceeding  on  this  basis  therefore  applied  themselves, 
not  to  the  problem  of  flying  as  a whole,  but  rather  divided  it 
into  its  elements,  and  sought  first  to  bring  a clear  understand- 
ing into  said  elements  which  should  form  the  basis  of  final 
success.  For  example,  take  the  laws  of  atmospheric  resistance, 
upon  which  all  flying  depends,  and  regarding  which,  until  very 
recent  years,  the  greatest  uncertainty  has  existed ; these  have 
now  been  defined  to  such  an  extent  that  the  different  phases 
of  flight  can  be  treated  mathematically.  Besides  which,  the 
physical  processes  of  the  natural  flight  of  the  creatures  have 
become  the  subject  of  minute  investigation,  and  have  in  most 
cases  been  satisfactorily  explained.  The  nature  of  the  wind 
also,  and  its  influence  on  flying  bodies,  have  been  carefully 

(7) 


8 


THE  AERONAUTICAL  ANNUAL. 


studied,  thus  enabling  us  to  understand  several  peculiarities  of 
the  birds’  flight  hitherto  unexplainable,  so  that  one  can  apply 
the  results  thus  obtained  in  perfecting  human  flight. 

The  theoretical  apparatus  needed  for  the  technics  of  flying 
has  been  enriched  so  much  by  all  these  studies  within  the  last 
few  years  that  the  elements  of  flying  apparatus  can  now  be 
calculated  and  constructed  with  sufficient  accuracy.  By  means 
of  this  theoretical  knowledge  one  is  enabled  to  form  and  con- 
struct wing-  and  sailing-surfaces  according  as  the  intended 
effect  renders  it  desirable. 

But  with  all  this,  we  are  not  yet  capable  of  constructing  and 
using  complete  flying  machines  which  answer  all  requirements. 
Being  desirous  of  furthering  with  all  speed  the  solution  of  the 
problem  of  flight,  men  have  repeatedly  formed  projects  in  these 
last  few  years  which  represent  complete  air-ships  moved  by 
dynamos ; but  the  constructors  are  not  aware  of  the  difficulties 
which  await  us  as  soon  as  we  approach  the  realizing  of  any 
ideas  in  flying. 

All  those,  who  have  occupied  themselves  to  any  extent  with 
actual  flying  experiments,  have  found  that,  even  if  they  mas- 
tered theoretically  the  problem  of  flying,  the  practical  solving 
of  the  same  can  only  be  brought  about  by  a gradual  and  weari- 
some series  of  experiments  based  one  upon  the  other. 

Also  the  practical  tasks  of  the  technics  of  flying  should  be 
simplified  and  divided  as  much  as  possible  instead  of  steering 
straight  to  the  final  goal. 

As  these  principles  have  been  seldom  carried  out,  the  practi- 
cal results  in  human  flight  have  remained  very  scanty  up  to  the 
present  day. 

One  can  get  a proper  insight  into  the  practice  of  flying  only 
by  actual  flying  experiments.  The  journey  in  the  air  without 
the  use  of  the  balloon  is  absolutely  necessary  in  order  to  gain  a 
judgment  as  to  the  actual  requirements  for  an  independent 
flight.  It  is  in  the  air  itself  that  we  have  to  develop  our  knowl- 
edge of  the  stability  of  flight  so  that  a safe  and  sure  passage 
through  the  air  may  be  obtained,  and  that  one  can  finally  land 
without  destroying  the  apparatus.  One  must  gain  the  knowl- 


DEVELOPMENT  OF  HUMAN  FLIGHT. 


9 


edge  and  the  capacity  needed  for  these  things  before  he  can 
occupy  himself  successfully  with  practical  flying  experiments. 

As  a rule  the  projectors  and  constructors  of  flying  machines 
have  not  gathered  this  absolutely  necessary  practical  experience, 
and  have  therefore  wasted  their  efforts  upon  complicated  and 
costly  projects. 

In  free  flight  through  the  air  a great  many  peculiar  phenom- 
ena take  place  which  the  constructor  never  meets  with  else- 
where ; in  particular,  those  of  the  wind  must  be  taken  into 
consideration  in  the  construction  and  in  the  employment  of 
flying  apparatus.  The  manner  in  which  we  have  to  meet  the 
irregularities  of  the  wind  when  soaring  in  the  air  can  only  be 
learnt  by  being  in  the  air  itself.  At  the  same  time  it  must  be 
considered  that  one  single  blast  of  wind  can  destroy  the  appara- 
tus and  even  the  life  of  the  person  flying.  This  danger  can  only 
be  avoided  by  becoming  acquainted  with  the  wind  by  constant 
and  regular  practice  and  by  perfecting  the  apparatus  so  that  we 
may  achieve  safe  flight. 

The  only  way  which  leads  us  to  a quick  development  in 
human  flight  is  a systematic  and  energetic  practice  in  actual 
flying  experiments.  These  experiments  and  exercises  in  flying 
must  not  only  be  carried  out  by  scientists,  but  should  also  be 
practised  by  those  wishing  for  an  exciting  amusement  in  the 
open  air,  so  that  the  apparatus  and  the  way  of  using  it  may  by 
means  of  common  use  be  quickly  brought  to  the  highest  possi- 
ble degree  of  perfection. 

The  question  is  therefore  to  And  a method  by  which  experi- 
ments in  flying  may  be  made  without  danger,  and  may  at  the 
same  time  be  indulged  in  as  an  interesting  amusement  by  sport- 
loving  men. 

Another  condition  is,  that  simple,  easily  constructed,  and 
cheap  apparatus  should  be  used  for  such  flying  exercises,  in 
order  to  conduce  to  a still  more  general  participation  in  this 
sport. 

All  these  conditions  are  easily  fulfilled.  One  can  fly  long 
distances  with  quite  simple  apparatus  without  taxing  one's 


lO 


THE  AERONAUTICAL  ANNUAL. 


strength  at  all,  and  this  kind  of  free  and  safe  motion  through 
the  air  affords  greater  pleasure  than  any  other  kind  of  sport. 

From  a raised  starting  point,  particularly  from  the  top  of  a flat 
hill,  one  can,  after  some  practice,  soar  through  the  air,  reaching 
the  earth  only  after  having  gone  a great  distance. 

For  this  purpose  I have  hitherto  employed  a sailing  apparatus 
very  like  the  outspread  pinions  of  a soaring  bird.  It  consists  of  a 
wooden  frame  covered  with  shirting  (cotton-twill).  The  frame 
is  taken  hold  of  by  the  hands,  the  arms  resting  between  cushions, 
thus  supporting  the  body.  The  legs  remain  free  for  running 
and  jumping.  The  steering  in  the  air  is  brought  about  by 
changing  the  centre  of  gravity.  This  apparatus  I had  con- 
structed with  supporting  surfaces  of  ten  to  twenty  square 
metres.  The  larger  sailing  surfaces  move  in  an  incline  of  one 
to  eight,  so  that  one  is  enabled  to  fly  eight  times  as  far  as  the 
starting  hill  is  high.  The  steering  is  facilitated  by  the  rudder, 
which  is  firmly  fastened  behind  in  a horizontal  and  vertical 
position. 

The  machines  weigh,  according  to  their  size,  from  15  to  25 
kilograms  (33  to  55  lbs.). 

In  order  to  practise  flying  with  these  sailing  surfaces  one  first 
takes  short  jumps  on  a somewhat  inclined  surface  till  he  has 
accustomed  himself  to  be  borne  by  the  air.  Finally,  he  is  able 
to  sail  over  inclined  surfaces  as  far  as  he  wishes. 

The  supporting  capacity  of  the  air  is  felt,  particularly  if  there 
is  a breeze.  A sudden  increase  in  the  wind  causes  a longer 
stoppage  in  the  air,  or  one  is  raised  to  a still  higher  point.. 

The  charm  of  such  flight  is  indescribable,  and  there  could  not 
be  a healthier  motion  or  more  exciting  sport  in  the  open  air. 

The  rivalry  in  these  exercises  cannot  but  lead  to  a constant 
perfecting  of  the  apparatus,  the  same  as,  for  instance,  is  the  case 
with  bicycles.  I speak  from  experience,  for,  although  the  sys- 
tem of  my  sailing  apparatus  remains  the  same,  it  has  gone 
through  numberless  changes  from  year  to  year.* 

The  apparatus  which  I now  employ  for  my  flying  exercises 

* See  article  entitled  " Wheeling  and  Flying." 


DEVELOPMENT  OF  HUMAN  FLIGHT. 


II 


contains  a great  many  improvements  as  compared  with  the  first 
sailing  surfaces  with  which  I commenced  this  kind  of  experi- 
ment five  years  ago.  The  first  attempts  in  windy  weather 
taught  me  that  suitable  steering  surfaces  would  be  needed  to 
enable  me  to  keep  my  course  better  against  the  wind.  Re- 
peated changes  in  the  construction  led  to  a kind  of  apparatus 
with  which  one  can  throw  himself  without  danger  from  any 
height,  reaching  the  earth  safely  after  a long  distance.  The 
construction  of  the  machine  is  such  that  it  resembles  in  all  its 
parts  a strut-frame,  the  joints  of  which  are  calculated  to  stand 
pull  and  pressure,  in  order  to  combine  the  greatest  strength  with 
the  least  weight. 

An  important  improvement  was  to  arrange  the  apparatus  for 
folding.  All  of  my  recent  machines  are  so  arranged  that  they 
can  be  taken  through  a door  2 metres  high.  The  unfolding 
and  putting  together  of  the  flying  implements  takes  about  two 
minutes. 

A single  grip  of  the  hands  is  sufficient  to  attach  the  apparatus 
safely  to  the  body,  and  one  gets  out  of  the  apparatus  just  as 
quickly  on  landing.  In  case  of  a storm  the  flying-sail  is  folded  up 
in  half  a minute  and  can  be  laid  by  anywhere.  If  one  should  not 
care  to  fold  the  apparatus,  he  may  await  the  end  of  the  storm 
under  cover  of  the  wings,  which  are  capable  of  protecting  twenty 
persons.  Even  the  heaviest  rain  will  not  damage  the  apparatus. 
The  flying  apparatus,  even  if  completely  drenched,  is  soon 
dried  by  a few  sailing  flights  after  the  rain  stops,  as  the  air 
passes  through  the  same  with  great  speed. 

The  latest  improvements  of  the  flying  apparatus  which  I use 
for  practical  experiments  refer  to  gaining  of  greater  stability  in 
windy  weather. 

My  experiments  tend  particularly  in  two  directions.  On  the 
one  side  I endeavor  to  carry  my  experiments  in  sailing 
through  the  air  with  immovable  wings  to  this  extent ; I practise 
the  overcoming  of  the  wind  in  order  to  penetrate,  if  possible, 
into  the  secret  of  continued  soaring  flight.  On  the  other  hand 
I try  to  attain  the  dynamic  flight  by  means  of  flapping  the 


.’3  V: 


^ "A 
A Ait* 


12 


THE  AERONAUTICAL  ANNUAL. 


wings,  which  are  introduced  as  a simple  addition  to  my  sailing 
flights.  The  mechanical  contrivances  necessary  for  the  latter, 
which  can  reach  a certain  perfection  only  by  gradual  develop- 
ment, do  not  allow  yet  of  my  making  known  any  definite 
results.  But  I may  state  that  since  my  sailing  flights  of  last 
summer,  I am  on  much  more  intimate  terms  with  the  wind. 

What  has  prevented  me  till  now  from  using  winds  of  any 
strength  for  my  sailing  experiments,  has  been  the  danger  of  a 
violent  fall  through  the  air,  if  I should  not  succeed  in  retaining 
the  apparatus  in  those  positions  by  which  one  insures  a gentle 
landing.  The  wildly  rushing  wind  tries  to  dash  about  the  free- 
floating  body,  and  if  the  apparatus  take  up  a position,  if  only  for 
a short  time,  in  which  the  wind  strikes  the  flying  surfaces  from 
above,  the  flying  body  shoots  downward  like  an  arrow,  and 
can  be  smashed  to  pieces  before  one  succeeds  in  attaining  a 
more  favorable  position  in  which  the  wind  exercises  a support- 
ing effect.  The  stronger  the  wind  blows,  the  easier  this  danger 
occurs,  as  the  gusts  of  wind  are  so  much  the  more  irregular  and 
violent. 

As  long  as  the  commotion  of  the  air  is  but  slight,  one  does 
not  require  much  practice  to  go  quite  long  distances  without 
danger.  But  the  practice  with  strong  winds  is  interesting  and 
instructive,  because  one  is  at  times  supported  quite  by  the  wind 
alone.  The  size  of  the  apparatus,  however,  unhappily  limits 
us.  We  may  not  span  the  sailing-surfaces  beyond  a certain 
measure,  if  we  do  not  wish  to  make  it  impossible  to  manage 
them  in  gusty  weather.  If  the  surfaces  of  14  square  metres  ^ do 
not  measure  more  than  7 metres^  from  point  to  point,  we  can 
eventually  overcome  moderate  winds  of  about  7 metres  ^ velocity, 
provided  one  is  well  practised.  With  an  apparatus  of  this  size 
it  has  happened  to  me  that  a sudden  increase  in  the  wind 
has  taken  me  way  up  out  of  the  usual  course  of  flying,  and  has 
sometimes  kept  me  for  several  seconds  at  one  point  of  the  air. 
It  has  happened  in  such  a case,  that  I have  been  lifted  vertically 
by  a gust  of  wind  from  the  top  of  the  hill  (shown  in  Fig.  3), 
floating  for  a time  above  the  same  at  a height  of  about  5 metres, 
whence  I then  continued  my  flight,  against  the  wind. 


* About  150  sq.  feet. 


^ About  23  feet. 


About  22  miles  per  hour. 


6R0V£R  C.  iS£M6iiOll 


Fig.  3. 


S|j  DEUTSCHES 


H PATENT  ,fe 


OTTO  LILIEITML 

Xraschmen  u-  Dampfkessel-Fabrik. 
Speeialitat:  GeTahrlose  Dampfkessel. 
Dampfmaschinen,  Heizungen,  Transraissionen,  schmiedeeiserne  Riemscheiben. 


Telephon: 

Amt  Vir.  No.  1626. 


(Q^ez/tn,  e/en  j. 

SO.,  Kspmicktr-Straist  113. 


-739^. 


C--  y*-»  fi-M.  ■*^*  ^ 


i 


DEVELOPMENT  OF  HUMAN  FLIGHT. 


13 


Although,  while  making  these  experiments  I was  thrown 
about  by  the  wind  quite  violently  and  was  made  to  execute 
quite  a dance  in  the  air  in  order  to  keep  my  balance,  I yet  was 
always  enabled  to  effect  a safe  landing,  but  still  I came  to  the 
conviction,  that  an  increase  in  the  size  of  the  wings  or  the  utiliz- 
ing of  still  stronger  winds  which  would  lengthen  the  journey  in 
the  air,  would  necessitate  something  being  done,  to  perfect  the 
steering  and  to  facilitate  the  management  of  the  apparatus. 
This  appeared  to  me  to  be  all  the  more  important  as  it  is  very 
necessary  for  the  development  of  human  flight  that  all,  who 
take  up  such  experiments,  should  quickly  learn  how  to  use  the 
apparatus  safely  and  understand  how  to  use  the  same  even  if 
the  air  is  disturbed.  It  is  in  the  wind  that  this  practice  becomes 
so  exciting  and  bears  the  character  of  a sport,  for  all  the  flights 
differ  from  each  other  and  the  adroitness  of  the  sailing-man  has 
the  largest  field  for  showing  itself.  Courage  also  and  decision 
can  be  here  shown  in  a high  degree. 

If  such  exercises  are  gone  through  with  in  a regular  and 
approved  method,  they  are  not  more  dangerous  than  if  one 
engages  in  riding,  or  sailing  on  the  water. 

Just  as  it  is  in  sports  on  the  water,  so  it  is  in  sports  in  the  air, 
that  the  greatest  aim  will  be  to  reach  the  most  startling  results. 
The  machines  themselves,  as  well  as  the  adroitness  of  their 
operators,  will  vie  with  each  other. 

He  who  succeeds  in  flying  the  farthest  from  a certain  starting- 
point,  will  come  forth  from  the  contest  as  conqueror.  This  fact 
will  necessarily  lead  to  the  production  of  more  and  more 
improved  flying  apparatus.  In  a short  time  we  shall  have  im- 
provements of  which  to-day  we  have  not  the  faintest  idea. 

The  foundation  for  such  a development  exists  already ; it 
only  needs  a more  thorough  carrying  out  to  gain  perfection. 
The  greater  the  number  is  of  such  persons  who  have  the  further- 
ing of  flying  and  the  perfecting  of  the  flying  apparatus  at  heart 
the  quicker  we  shall  succeed  in  reaching  a perfect  flight.  It  is 
therefore  of  paramount  importance  that  as  many  physically  and 
technically  well-trained  men  as  possible  take  interest  in  these 


14 


THE  AERONAUTICAL  ANNUAL. 


affairs,  and  that  an  apparatus  be  constructed  which  is  as  con- 
venient and  as  cheap  as  possible. 

The  means  by  which  I sought  to  facilitate  the  management  of 
the  machines  and  to  increase  their  use  in  wind,  consisted  in  the 
first  place  in  different  arrangements  for  changing  the  shape  of 
the  wings  at  will.  I will,  however,  pass  over  the  results  here 
obtained  as  another  principle  gave  surprisingly  favorable  results. 

My  experiments  in  sailing  flight  have  accustomed  me  to 
bring  about  the  steering  by  simply  changing  the  centre  of 
gravity. 

The  smaller  the  surface  extension  of  the  apparatus  is,  the 
better  control  I have  over  it,  and  yet  if  I employ  smaller  bearing 
surfaces  in  stronger  winds,  the  results  are  not  more  favorable. 
The  idea  therefore  occurred  to  me  to  apply  two  smaller  surfaces, 
one  above  the  other,  which  both  have  a lifting  effect  when  sail- 
ing through  the  air.  Thus  the  same  result  must  follow  which 


would  be  gained  by  a single  surface  of  twice  the  bearing 
capacity,  but  on  account  of  its  small  dimensions  this  apparatus 
obeys  much  better  the  changes  of  the  centre  of  gravity. 

Before  I proceeded  to  construct  these  double-sailing  machines, 
I made  small  models  in  paper  after  that  system,  in  order  to 
study  the  free  movements  in  the  air  of  such  flying  bodies  and 
then  to  construct  my  apparatus  on  a large  scale,  depending  on 


DEVELOPMENT  OF  HUMAN  FLIGHT. 


15 


the  results  thus  obtained.  The  very  first  experiments  with 
these  small  models,  the  form  of  which  may  be  seen  in  Figs,  i 


and  2,  surprised  me  greatly  on  account  of  the  stability  of  their 
flight.  It  appears  as  if  the  arrangement  of  having  one  surface 
over  the  other  had  materially  increased  the  safety  and  uni- 
formity of  the  flight.  As  a rule  it  is  rather  difficult  to  produce 
models  resembling  birds,  which,  left  to  themselves,  glide  through 
the  air  from  a higher  point  in  uniformly  inclined  lines.  I need 
only  recall  the  extensive  and  expensive  experiments  made  by 
Messrs.  Riedinger,  von  Sigsfeld,  and  von  Parsefal,  of  Augsburg, 
which  showed  the  difficulty  of  constructing  models  that  would 
automatically  take  up  a course  of  stable  flight.  I myself 
doubted  formerly  very  much  that  an  inanimate  body  sailing 
quickly  forward,  could  be  well  balanced  in  the  air,  and  was  all 
the  better  pleased  in  succeeding  in  this  with  my  little  double 
surfaces. 

Relying  on  this  experience  I constructed  first  a double  appa- 
ratus (Fig.  3),  in  which  each  surface  contains  9 square  metres.^ 
I thus  produced  a comparatively  large  bearing  surface  of  18 
square  metres  with  but  5 >4  metres^  span. 

The  upper  surface  is  separated  from  the  lower  by  a distance 
equal  to  three  quarters  of  the  breadth  of  the  lower  surface,  and 
it  has  no  disturbing  influence  whatever,  but  creates  only  a verti- 
cally acting  lifting  force.  One  must  consider  that  with  such  an 
apparatus  one  always  cuts  the  air  quickly,  so  that  both  surfaces 
are  met  by  the  air-current,  and  therefore  both  act  as  lifters. 

The  whole  management  of  such  an  apparatus  is  just  the 
same  as  that  of  a single  sailing  surface.  I could,  therefore,  use 
at  once  the  skill  I had  already  obtained. 

The  figures  show  how  I change  the  centre  of  gravity,  and 


1 About  97  sq.  feet. 


•About  18  feet. 


i6 


THE  AERONAUTICAL  ANNUAL. 


particularly  the  position  of  the  legs  in  order  to  press  down 
either  wing.  I retain  the  middle  position,  as  shown  in  the 
frontispiece,  whenever  the  apparatus  floats  horizontally. 

The  flights  undertaken  with  such  double  sailing  surfaces  are 
distinguished  by  their  great  height,  as  is  shown  in  Fig.  6,  which 
gives  a side-view  of  the  apparatus. 

The  landing  with  this  apparatus  is  brought  about  in  the  same 
way  as  with  the  single  sailing  surfaces  by  raising  the  apparatus 
in  front  somewhat  and  by  lessening  the  speed,  as  shown  in 
Fig-  7- 

Fig.  8 shows  an  exact  picture  of  the  construction  of  the 
apparatus,  as  well  as  of  the  management  of  the  same. 

The  energetic  effect  of  the  change  of  the  centre  of  gravity 
and  the  safe  starting  of  the  apparatus  obtained  by  it  gave  me 
courage  to  trust  myself  to  a wind  which  at  times  exceeded  a 
velocity  of  lO  metres  (about  24  miles  per  hour). 

This  gave  the  most  interesting  results  of  all  my  practical 
flying  experiments  hitherto.  Six  or  seven  metres  velocity  of 
wind  sufficed  to  enable  the  sailing  surface  of  18  square  metres 
to  carry  me  almost  horizontally  against  the  wind  from  the  top 
of  my  hill  without  any  starting  jump.  If  the  wind  is  stronger,  I 
allow  myself  to  be  simply  lifted  from  the  point  of  the  hill  and 
to  sail  slowly  towards  the  wind.  The  direction  of  the  flight  has, 
with  strong  wind,  a strong  upward  tendency.  I often  reach 
positions  in  the  air  which  are  much  higher  than  my  starting- 
point.  At  the  climax  of  such  a line  of  flight  I sometimes  come 
to  a standstill  for  some  time,  so  that  I am  enabled  while  floating 
to  speak  with  the  gentlemen  who  wish  to  photograph  me,  re- 
garding the  best  position  for  the  photographing.^ 

At  such  times  I feel  plainly  that  I would  remain  floating  if  I 
leaned  a little  towards  one  side,  described  a circle  and  proceeded 
with  the  wind.  The  wind  itself  tends  to  bring  this  motion 
about,  for  my  chief  occupation  in  the  air  consists  in  preventing 

^The  photographs  were  made  by  Drs.  Neuhaus  and  Fiilleboni,  who  used  a camera  con- 
structed by  Dr.  Neuhaus  on  the  Stegemann  principle. 


Plate  ///, 


Fig.  5. 


Fig.  6. 


fl 


DEVELOPMENT  OF  HUMAN  FLIGHT, 


17 


a turn  either  to  right  or  the  left,  and  I know  that  the  hill  from 
which  I started  lies  behind  and  underneath  me,  and  that  I might 
come  into  rough  contact  with  it  if  I attempted  circling.  My 
endeavors  tend  therefore  to  remove  myself  farther  from  the  hill 
either  by  increased  wind  or  by  flapping  with  the  wings,  so  that 
I can  follow  the  strongly  lifting  air-current  in  a circle,  and  so 
that  I can  have  a sufficient  space  of  air  under  and  beside  me  to 
succeed  in  describing  with  safety  a circling  flight  and  to  land 
finally  steering  against  the  wind. 

As  soon  as  I or  any  other  experimenter  succeeds  in  de- 
scribing the  first  circling  flight,  one  may  regard  this  event  as 
one  of  the  most  important  conquests  on  the  road  to  perfect 
flight.  From  this  moment  only,  one  is  enabled  to  make  a 
thorough  use  of  the  vis  viva  of  the  wind,  so  that  when  the  wind 
increases  one  is  able  to  steer  against  it,  and  when  it  decreases 
one  can  fly  with  it,  getting  beyond  the  same.  One  will  feel  here 
a similar  effect,  as  already  described  by  Professor  Langley  in 
his  celebrated  treatise  entitled  “The  Internal  Work  of  the 
Wind.”  It  is  no  easy  step  from  the  theoretical  conviction  to  the 
practical  execution.  The  dexterity  required  to  allow  one’s  self  to 
be  borne  by  the  wind  alone,  by  describing  well-directed  circles, 
is  only  understood  by  those  who  are  well  acquainted  with  the 
difficulties  one  encounters  with  the  wind.  And  yet  all  that  may 
be  acquired  by  practice.  When  the  time  comes  that  athletic 
associations  emulate  each  other,  such  results  will  not  be  long 
in  following. 

Moreover,  experimenters  will  proceed  from  simple  floating 
and  sailing,  which  in  any  case  form  the  foundation  for  practical 
flight,  by  degrees  to  flying  with  movable  implements.  As  one  is 
enabled  to  balance  himself  for  some  time  in  the  air,  the  foun- 
dations for  more  extended  dynamic  effects  are  easily  and  safely 
attained.  The  different  projects  may  be  easily  tried  by  adding 
the  motor  work  to  the  simple  sailing  flight  taken  as  a basis. 
In  this  manner  one  will  soon  find  out  the  best  methods ; for 
practical  experience  in  the  air  is  far  better  than  figuring  on 
paper. 

The  only  thing  which  may  cause  difficulties  is  the  procuring 
of  a suitable  place  for  practising. 


i8 


THE  AERONAUTICAL  ANNUAL. 


Just  as  the  starting  from  the  earth  is  rather  difficult  for  larger 
birds,  the  human  body,  being  still  heavier,  meets  with  peculiar 
difficulties  at  the  first  flight  upward.  The  larger  birds  take 
a running  start  against  the  wind  or  throw  themselves  into  the 
air  from  elevated  points,  in  order  to  obtain  free  use  of  their 
pinions.  As  soon,  however,  as  they  float  in  the  air,  their  flight, 
which  was  begun  under  special  difficulties,  is  easily  continued. 
The  case  is  similar  in  human  flight.  The  principal  difficulty  is 
the  launching  into  the  air,  and  that  will  always  necessitate  special 
preparations.  A man  will  also  have  to  take  a running  start 
against  the  wind  with  his  flying  apparatus,  but  on  a horizontal 
surface  even  that  will  not  be  sufficient  to  free  himself  from  the 
earth.  But,  on  taking  a running  start  from  a correspondingly 
inclined  surface,  it  is  easy  to  begin  one’s  flight  even  if  there  is 
no  wind. 

According  to  the  example  of  birds,  man  will  have  to  start 
against  the  wind ; but  as  an  inclined  surface  is  necessary  for 
this  he  needs  a hill  having  the  shape  of  a flat  cone,  from  the 
top  of  which  he  may  take  starts  against  the  wind  in  any  direc- 
tion. 

Such  a place  is  absolutely  necessary,  if  one  wishes  to  make 
flying  experiments  in  a convenient  way  without  being  depend- 
ent on  the  direction  of  the  wind. 

For  this  purpose  I have  had  an  artificial  hill,  1 5 metres 
high,  erected  near  my  house  in  Gross  Lichterfelde,  near  Berlin, 
and  so  have  been  enabled  to  make  numerous  experiments. 
The  drawings  show  this  hill,  or  part  of  the  same,  from  the  out- 
side. Fig.  9 represents  a section  of  it,  showing  the  cavity  in  the 
top  intended  for  keeping  the  apparatus.  At  the  same  time  the 
line  of  flight  taken  in  calm  weather  is  shown  by  dotted  lines. 

If  a place  for  this  sport  is  procured  where  young  persons 
wishing  to  indulge  in  flight  can  disport  themselves  in  the  air, 
they  will  then  have  a chance  to  make  instructive  and  interest- 
ing sailing  flights,  and  I should  advise  having  the  hill  bvice 
as  high,  and  to  form  it  according  to  Fig.  10,  so  that  one  can 
commence  the  flights  from  a height  of  30  metres.  The 
cavity  inside  should  be  large  enough  to  hold  several  complete 
machines. 


Plate  IV. 


F.g.  7. 


Fig.  8, 


DEVELOPMENT  OF  HUMAN  FLIGHT. 


19 


From  such  a hill  one  can  take  flight  of  200  metres  distance, 
and  the  floating  through  the  air  on  such  long  distances  affords 
indescribable  pleasure.  Added  to  which  this  highly  exciting 
exercise  is  not  dangerous,  as  one  can  effect  a safe  landing  at 
any  time. 

Such  a place  in  which  young  men  can  practise  sailing  flights 
and  can  at  times  make  motor  experiments  with  the  wings  would 
prove  to  be  of  great  interest,  both  to  those  participating  and  to 
the  public  in  general. 

And  when,  from  time  to  time,  competitive  flights  were  ar- 
ranged, we  should  soon  have  a national  amusement  in  this  as  in 
other  sports  which  we  have  already.  One  can  see  even  now 
that  the  pleasure  and  interest  of  the  public  in  such  races,  when 
the  gymnasts  skilled  in  flights,  shoot  through  the  air,  would  be 
greater  and  more  intense  than,  for  instance,  in  horse  or  boat 
racing.  The  air  is  the  freest  element;  it  admits  of  the  most 
unfettered  movement,  and  the  motion  through  it  affords  the 
greatest  delight  not  only  to  the  person  flying,  but  also  to  those 
looking  on.  It  is  with  astonishment  and  admiration  that  we  fol- 
low the  air  gymnast  swinging  himself  from  trapeze  to  trapeze ; 
but  what  are  these  tiny  springs  as  compared  to  the  powerful 
bound  which  the  sailer  in  the  air  is  able  to  take  from  the  top 
of  the  hill,  and  which  carries  him  over  the  ground  for  hundreds 
of  yards  ? 

If  the  atmosphere  is  undisturbed,  the  experimenter  sails  with 
uniform  speed  ; as  soon,  however,  as  even  a slight  breeze  springs 
up,  the  course  of  the  flight  becomes  irregular,  as  indicated  in 
Fig.  10.  The  apparatus  inclines  now  to  the  right,  now  to  the 
left. 

The  person  flying  ascends  from  the  usual  line  of  flight,  and, 
borne  by  the  wind,  suddenly  remains  floating  at  a point  high  up 
in  the  air ; the  on-lookers  hold  their  breath ; all  at  once 
cheers  are  heard,  the  sailer  proceeds  and  glides  amid  the  joyful 
exclamations  of  the  multitude  in  a graceful  curve  back  again  to 
the  earth. 

Can  any  sport  be  more  exciting  than  flying?  Strength  and 
adroitness,  courage  and  decision,  can  nowhere  gain  such  tri- 


20 


THE  AERONAUTICAL  ANNUAL. 


umphs  as  in  these  gigantic  bounds  into  the  air,  when  the  gym- 
nast safely  steers  his  soaring  machine  house-high  over  the  heads 
of  the  spectators. 

That  the  danger  here  is  easily  avoided  when  one  practises  in 
a reasonable  way,  I have  sufficiently  proved,  as  I myself  have 
made  thousands  of  experiments  within  the  last  five  years,  and 
have  had  no  accidents  whatever,  a few  scratches  excepted. 

But  all  this  is  only  a means  to  the  end ; our  aim  remains  — the 
developing  of  human  flight  to  as  high  a standard  as  possible. 
If  we  can  succeed  in  enticing  to  the  hill  the  young  men  who 
to-day  make  use  of  the  bicycle  and  the  boat  to  strengthen  their 
nerves  and  muscle,  so  that,  borne  by  their  wings,  they  may 
glide  through  the  air,  we  shall  then  have  directed  the  develop- 
ment of  human  flight  into  a course  which  leads  towards  per- 
fection. 


OROVEa  C. 


R£Ra&ii,i 

Plate  It. 


o\ 


L 


£ 

il 


[From  Aeko.  Ann.,  1896.J 


WHEELING  AND  FLYING. 

By  the  Editor. 


The  slow  development  of  the  flying  machine  in  its  early 
stages  finds  its  analogue  in  that  of  the  bicycle.  The  admirable 
wheel  of  to-day  is  the  product  of  more  than  eighty  years  of  care- 
ful thought  and  experiment. 

The  machine  has  been  improved  very  gradually ; most  of  the 
modifications  have  been  slight;  yet  some  of  the  stages  have 
been  marked  with  great  distinctness. 

The  twelve  machines  here  shown  in  the  drawings  give  a 
rough  outline  of  the  progress  made.  First,  we  have  the  wheel 
of  1816  (Fig.  l),  propelled  by  striking  the  feet  against  the 
ground.  This  machine  represents  the  parent  form,  involving 
the  great  principle  of  two  wheels  balanced  by  the  act  of  turn- 
ing the  forward  wheel  on  a pivot.  It  was  used  principally  for 
the  purposes  of  sport,  and  it  is  easily  seen  that  it  was  at  its  best 
on  down  grades. 

Looking  backward,  it  seems  strange  to  us  that  a device  so 
simple  as  a pair  of  foot  cranks  attached  to  the  front  axle  was 
not  soon  adopted,  yet  the  discovery  of  such  simple  things  some- 
times takes  years  of  hard  thinking.  Columbus  was  doubtless 
surprised  when  the  superficial  people  of  his  day  told  him  on  his 
return  that  any  sailor  might  have  discovered  the  distant  land, 
“ all  one  had  to  do  was  to  sail  west.”  His  alleged  reply,  illus- 
trated by  the  balancing  of  the  egg,  was  most  appropriate.  The 
inventor  of  the  sewing  machine  informed  the  world  that  all 
through  the  centuries  the  sewing  needle  had  been  threaded  at 
the  wrong  end ; no  one  knows  how  long  it  took  him  to  think 
that  out.  We  do  know,  however,  in  the  case  of  the  wheel, 
that  it  took  many  years  to  think  of  putting  foot  cranks  on  the 
front  axle. 


(21) 


22 


THE  AERONAUTICAL  ANNUAL. 


Mr.  Porter  says  * that  in  1821  Gompertz  invented  the  “Hobby 
Horse”  shown  in  Fig.  2,  and  that  in  1840  McMillan  made  a 
rear-driving  machine  as  shown  in  Fig.  3. 

He  quotes  M.  de  Saunier  as  saying  that  the  honors  of  first 
applying  foot  cranks  to  the  front  axle  seem  to  be  evenly  divided 
between  Michaux  and  Lallement,  who  probably  worked  inde- 
pendently of  each  other,  the  former  applying  the  cranks  in 
1855,  the  latter  in  1863. 

Lallement’s  machine  of  1866  is  shown  in  Fig.  4.  This  was 
the  machine  which  immediately  preceded  the  velocipede  excite- 
ment of  the  late  sixties. 

Fig.  5 shows  the  improvement  made  from  1866  to  1869. 

Mr.  Porter  says,  “ In  1871  W.  H.  J.  Grant  proposed  the  use 
of  rubber  pedals,  . . . and  he  also  vulcanized  rubber  tires 

into  crescent-shaped  metal  rims.” 

“ In  1873  there  was  produced  by  Starley,  ‘the  Father  of  the 
Bicycle,’  about  the  first  machine  (Fig.  6)  embodying  most  of 
the  features  which  are  found  in  the  modern  Ordinary.” 

The  Ordinary  was  greatly  improved  in  the  ten  or  twelve  suc- 
ceeding years  (see  Fig.  7),  and  long  distance  riding  became 
common,  yet  the  dangers  attending  the  use  of  the  high  machine 
gradually  led  to  the  designing  of  lower  wheels,  of  which  types 
are  shown  in  Figs.  8,  9,  lO,  and  ll. 

Later  came  the  safety  with  cushion  tires,  which  was  followed, 
at  last,  by  the  pneumatic  Safety  of  to-day  (Fig.  12).  This  is 
a mere  outline ; the  intermediate  machines  were  many. 

It  is  not  uncommon  for  the  cyclist,  in  the  first  flush  of  en- 
thusiasm which  quickly  follows  the  unpleasantness  of  taming 
the  steel  steed,  to  remark,  “ Wheeling  is  just  like  flying  ! ” This 
is  true  in  more  ways  than  one.  Let  us  note  the  points  of  re- 
semblance. Both  modes  of  travel  are  riding  upon  the  air, 
though  in  one  case  a small  quantity  of  air  is  carried  in  a bag 
and  in  the  other  the  air  is  unbagged.  There  are  many  who 

* See  WAee/s  and  Wheeling,  by  Luther  H.  Porter.  Published  by  The  tVheelman  Co., 
12  Pearl  st.,  Boston.  387  pp.  75  cents.  The  editor  of  The  Annual  is  indebted  to  the  author 
of  the  above  interesting  and  valuable  work  for  the  principal  facts  concerning  bicycles  men- 
tioned in  this  article.  The  cuts  i to  ii  are  taken  from  Mr.  Porter’s  book,  he  having 
kindly  consented  to  their  reproduction. 


Plate  VI. 


THE  DEVELOPMENT  OF  THE  WHEEL. 


WHEELING  AND  FLYING. 


23 


believe  that  in  order  to  travel  upon  air  it  is  not  necessary  to  put 
the  air  in  a bag ; they  not  only  believe  this  but  they  know  it  has 
been  done.  Lilienthal  has  done  it  many  times,  and  the  Lilien- 
thal  machine  is  to  flying,  what  the  wheel  of  1816  was  to  pneu- 
matic wheeling.  The  Lilienthal  machine  seems  likely  to  lead  to 
important  things,  yet  there  are  men  who  say  of  the  inventor : 
“ He  cannot  fly  up,  he  can  only  fly  down,  he  is  a parachutist,  a 
flying  squirrel,  he  has  not  solved  the  great  problem.”  True,  he 
has  not  solved  it,  but  he  has  given  a partial  solution  which  will 
place  his  name  on  the  roll  of  the  immortals. 

It  is  not  unlikely  that  men  regarded  the  wheel  of  1816  as 
some  now  regard  the  Lilienthal  soarer.  They  probably  said, 
“ This  machine  will  do  for  coasting  down  hill,  but  that  is  not 
practical  travelling.  You  cannot  climb  hills  with  the  thing ; it 
is  not  of  much  importance  anyhow.”  But  after  a while,  one 
day  a man  who  thought  put  cranks  on  that  machine  ! 

Lilienthal  flies  not  only  down,  but  also  up.  His  course  as  a 
whole  is  downward,  but  when  under  favoring  winds  he  gets 
energy  from  beneath  he  rises.  The  only  reason  that  his  course 
as  a whole  is  not  upward  is  that  he  has  not  yet  completed  his 
apparatus  for  giving  constant  energy. 

That  will  take  time,  and  if  the  world  is  to  make  rapid  prog- 
ress in  manflight  it  must  have  a much  greater  confidence  in 
the  value  and  importance  of  the  Lilienthal  soarer  than  it  had  in 
the  wonderful  balancing  wheel  of  1816.  It  was  a balancing 
wheel,  and  the  great  art  of  balancing  began  with  it.  To  learn 
to  wheel  one  must  learn  to  balance ; to  learn  to  fly  one  must 
learn  to  balance.  Why  not  begin  now,  instead  of  imitating  the 
human  race  of  the  first  half  of  the  century  which  took  so  many 
years  to  get  its  feet  off  the  ground  ? 


[From  Aero.  Ann.,  1897.] 


OUR  TEACHERS  IN  SAILING  FLIGHT. 

By  Otto  Lilienthal. 

Tratislated  from  Prometheus. 


I HAVE  recently  seen  such  wondrous  feats  performed  in 
sailing  flight  that,  as  I now  sit  at  my  table  to  write,  I do  so 
with  more  enthusiasm  than  ever  before;  for  the  things  which 
I have  seen  prove  clearly  and  deflnitely  that  flight  must  be 
much  easier  than  it  is  generally  believed  to  be,  if  we  only,  with 
suitable  wings,  boldly  trust  ourselves  to  the  wind.  All  per- 
plexities concerning  light  motors,  and  speculations  on  the 
amount  of  power  required  for  flying,  are  relegated  to  the  back- 
ground by  the  fact  that  the  power  of  the  wind  alone  is  suffi- 
cient to  effect  any  kind  of  independent  flight. 

If  we  had  not  those  magnificent  models  in  flying,  those  large 
and  heavy  birds  which,  without  a flap  of  the  wing,  allow  them- 
selves to  be  borne  by  the  wind,  doubters  would  be  justified, 
and  we  should  lack  the  courage  to  attempt  the  solution  of  the 
problem  with  the  perseverance  which  is  necessary ; but,  as 
it  is,  the  tangible  results  cannot  be  denied,  there  is  a flight 
which  does  not  require  any  effort,  where  only  the  shape  and 
position  of  the  wings  must  be  right  in  order  to  float,  circle,  or 
sail  in  the  air  at  any  height  or  in  any  direction  desired ; there- 
fore our  confidence,  notwithstanding  many  vain  attempts,  is 
always  renewed. 

But  which  are  the  birds  best  fitted  as  models  in  soaring 
flight?  How  can  we  best  find  a position  for  making  fruitful 
observations? 

If  we  go  through  the  fields  in  summer,  we  see  now  and  then 
a bird  of  prey  circling  about ; then  a swamp  bird,  of  the  larger 
kind,  passing  along  arrests  our  attention : yet  if  one  goes  out 
on  purpose  for  such  observations,  it  may  be  that  he  will  lie  in 

(24) 


OUR  TEACHERS  IN  SAILING  FLIGHT. 


wait  for  days  in  vain,  or  if  a sailing  bird  comes  in  sight,  it  is 
very  likely  high  up  in  the  heavens  and  far  away,  so  that  little 
can  be  learned  from  it. 

The  Americans  are  proud  of  their  buzzard  which  gives  them 
such  exhibitions  in  the  art  of  soaring,  but  in  order  to  observe 
this  near  at  hand  and  to  be  able  to  study  the  effect  of  soaring, 
places  of  concealment  must  be  arranged  in  the  tops  of  trees  and 
in  rocks  from  which  the  observer  may  watch  the  motions  of 
flight. 

Things  are  easier  for  people  living  on  the  coast;  the  graceful 
soaring  flight  of  the  gulls  can  be  frequently  observed  near  at 
hand,  as  these  birds  are  not  very  timid,  from  their  being  so  sel- 
dom hunted.  But  the  best  opportunity  for  studying  soaring 
flight  is  to  be  had  in  the  lowlands  of  Northern  Germany,  in  the 
villages,  where  the  stork  lives  his  family  life  on  the  low  roofs, 
unconcernedly  showing  off  his  art  close  above  the  heads  of  ob- 
servers, and  by  his  size  giving  the  observer  the  clearest  impres- 
sions of  the  shape  and  position  of  the  wings. 

But  even  at  these  stork  nests  it  is  tedious  to  wait  for  the 
moment  when  the  old  birds  return  with  food  for  their  young ; it 
is  generally  only  for  a short  moment,  in  the  quick  coming  and 
going,  that  one  can  observe  closely  the  flying  or  the  soaring 
stork. 

Observation  is  more  productive  when  the  young  birds  are 
fledging.  As  soon,  however,  as  they  have  learned  to  soar,  which 
soon  happens  in  windy  weather,  they  do  not  remain  in  the  vicin- 
ity of  the  nest,  and  one  can  look  for  them  a long  time  in  vain. 

Being  convinced  that  Father  Longlegs  is  just  made  for  our 
instructor  in  flying,  I kept  a great  many  young  storks  some 
years  ago,  whose  attempts  at  flying  have  given  me  many  expla- 
nations in  flying  technics.  As  soon,  however,  as  their  proflciency 
extended  to  soaring,  when  rising  above  the  tree-tops,  they  felt  the 
magnificent  bearing-effect  of  the  wind,  and  ventured  into  higher 
regions,  they  joined  other  wild  storks,  and  so  ended  all  further 
observation. 

While  on  a journey  to  procure  these  young  storks  a friendly 
man  told  me  that  there  could  be  no  better  place  for  observing 


26 


THE  AERONAUTICAL  ANNUAL. 


these  birds  than  the  village  of  Vehlin,  near  Gldwen,  on  the 
Berlin-Hamburg  railroad,  for  there  there  were  on  every  roof 
two  or  three  stork  nests,  and  hundreds  of  storks  circled  above 
them. 

This  address  slumbered,  probably,  seven  years  in  my  note- 
book, till  last  Easter  I made  use  of  the  fine  days  to  take  a trip, 
in  company  with  my  two  boys,  to  Vehlin.  The  road  — a two 
hours’ walk — from  the  station  of  Gldwen  led  us  through  villages 
in  no  way  distinguished  by  a wealth  of  storks.  I began  to 
think  the  good  man  had  played  us  a joke.  But  on  approach- 
ing the  village  of  Vehlin,  my  two  boys  cried  out,  “ Why,  there 
is  a stork’s  nest ! ” “ There’s  another  ! ” “ And  another  ! ” 

“ There  are  two  on  one  roof  ! ” “ Yonder  are  two  more  ! ” Our 

friendly  adviser  was  quite  right,  for  on  the  forty  houses  of  this 
little  village  were  no  less  than  fifty-four  storks’  nests,  about  some 
of  which  the  single  pairs  were  yet  fighting,  while  in  some  the 
process  of  hatching  had  already  commenced. 

With  the  exception  of  an  interesting  combat  between  the 
male  storks  which,  rolled  up  like  a ball,  often  rolled  off  the 
roof,  only  separating  in  a fright  on  dropping  into  the  yard, 
there  was  not  much  to  be  seen  that  day.  Yet  I was  glad  to 
know  of  a place  where  in  mid-summer,  when  the  young  storks 
are  fully  grown,  the  most  magnificent  exercises  in  flying  would 
be  observable.  I was  not  mistaken.  On  going  again  to  Vehlin 
in  August,  almost  the  entire  army  of  storks  was  to  be  seen  in 
the  air  over  the  village.  The  day  was  sunny  and  windy,  just 
suitable  for  studying  the  soaring  of  these  immense  birds. 

My  observations  result,  so  far,  in  ascertaining  that  in  windy 
weather,  when  the  air  in  the  lower  strata  has  a velocity  of  about 
six  to  eight  metres,  the  stork  does  not  move  its  wings  at  all, 
and  proceeds  soaring  or  sailing  in  the  air. 

This  soaring  took  place  not  only  close  above  the  roofs  of  the 
houses,  but  also  at  so  great  a height  that  it  was  difficult  to  fol- 
low the  birds’  motion  with  the  naked  eye.  The  birds  flapped 
their  wings  only  when  moving  between  the  houses  or  trees  — 
that  is,  in  places  protected  from  the  wind.  They  soared  in  any 
direction  they  pleased,  against  the  wind,  with  the  wind,  or  side- 


GROVER  C.  BERGDOLL 

OUR  TEACHERS  IN  SAILING  FLIGHT.  2/ 


wise.  They  circled  in  order  to  ascend  quickly  to  higher  air 
strata. 

When  instructing  their  young  the  storks  fly  mostly  in  smaller 
or  larger  companies,  at  different  heights,  flying  over  the  village 
alternately  with  or  against  the  wind.  In  some  of  the  nests 
young  birds  were  standing,  which  did  not  yet  take  part  in  the 
exercises.  As  soon  as  these  latter  saw  their  relatives  fly  away 
above  them  they  would  greet  them  in  their  own  peculiar 
language,  by  laying  their  heads  on  their  backs  and  rattling 
with  their  beaks.  Generally  some  of  those  flying  would  de- 
scend from  the  rest  to  their  young  ones  in  the  nest.  If  the 
flight  in  doing  this  had  to  be  made  from  a great,  windy  height, 
it  gave  the  impression  that  the  stork  found  the  descent  more 
trying  than  the  ascent. 

To  descend  more  rapidly  the  stork  employs  various  ma- 
nceuvres.  The  simplest  is  that  of  letting  the  legs  hang,  thus 
lessening  the  soaring  effect  by  a resistance  to  the  air.  With  a 
good  sailing-wind,  however,  these  means  are  insufflcient,  and 
head  and  neck  have  to  be  lowered,  at  the  same  time  the  wings 
are  bent  so  low  down  as  to  form  the  perfect  shape  of  a bell. 
This  position,  however,  appears  to  cause  the  stork  an  effort,  as 
it  soon  changes  again  to  the  outspread  position.  On  attaining 
this,  however,  it  again  commences  to  ascend,  and  then  it  is  seen, 
after  a few  vain  efforts  to  come  down  quickly  from  the  height, 
to  employ  a radical  means  for  rapid  descent.  This  consists  of 
placing  itself  in  a vertical  plane ; that  is,  with  the  point  of  one 
wing  underneath,  the  point  of  the  other  above.  In  this  manner 
it  can,  of  course,  shoot  downwards  like  an  arrow.  In  its  down- 
ward rush,  however,  it  changes  several  times  from  the  right 
position  to  the  left.  Finally  it  takes  once  more  the  position 
of  the  bell,  till  it  lands  on  the  nests,  where  it  is  always  received, 
after  such  feats  of  prowess,  with  a joyful  rattle. 

A good  deal  could  be  said  about  these  drops,  often  from  a 
height  of  several  hundred  metres,  but  we  have  less  interest  in 
the  descent  from  the  height  than  in  the  art  of  balancing  in  the 
air  simply  by  means  of  outspread  wings. 

In  order  to  observe  this  proficiency  frequently  close  to,  we 


28 


THE  AERONAUTICAL  ANNUAL. 


chose  a point  of  observation  on  a farm  which  was  blest  with  five 
stork-nests,  and  from  where  we  could  oversee  a dozen  others. 

The  only  means  of  lifting  the  last  veil  from  the  mystery  of 
soaring  is  to  be  able  to  frequently  observe  large  birds  at  a near 
distance  in  their  soaring  flight. 

Three  things  are  essential  for  soaring:  a correct  shape  of 
wing,  the  right  position  of  wing,  and  a suitable  wind.  In  order 
to  judge  of  these  three  factors  and  their  changeable  effect,  we 
have  nothing  but  our  practised  eye  to  depend  upon. 

Just  how  much  the  cross-section  of  the  wing  is  arched  when 
the  stork  is  resting  on  the  wind  can  be  determined  only  by  eye 
measurement;  similarly  the  position  of  the  wing  to  the  direction 
of  the  wind  and  to  the  horizon.  But  when  hundreds  of  storks 
give  one  the  opportunity  to  observe  the  same  in  clear  weather 
close  at  hand,  what  is  seen  is  impressed  so  indelibly  on  the  mind 
that  it  enables  one  to  draw  correct  conclusions  as  to  the  exist- 
ing laws. 

In  general,  one  can  say  that  when  the  stork  flies  with  wings 
spread  horizontally  and  allows  itself  to  be  borne  by  the  wind 
alone,  it  is  but  seldom  that  a stronger  gust  of  wind  causes  the 
stork  to  draw  in  its  wings. 

The  parabolic  profile  of  the  wings  has  a depth  which  I con- 
sider to  be  about  of  the  breadth  of  the  wing.  The  pinions 
are  mostly  spread  out,  but  do  not  lie  in  one  plane ; but  the 
more  they  are  to  the  front,  the  higher  are  the  points,  certainly 
because  they  would  otherwise  hinder  one  another  in  their 
bearing  capacity. 

When  in  this  position  the  stork  passes  slowly  against  the 
wind  above  the  observer,  the  head  and  neck  are,  as  a rule, 
stretched  straight  out ; but  if  one  imagines  that  soaring  is  pos- 
sible in  this  position,  that  it  causes  little  resistance,  he  will  be 
surprised  to  see  a stork,  sailing  in  this  manner,  suddenly,  with- 
out changing  its  position,  lay  its  head  back  and  rattle  joyously. 
While  we  human  beings  are  striving  to  find  the  proper  shape 
for  the  wings,  building  theory  on  theory,  flying  takes  place 
in  nature  in  a wondrously  simple  way,  quite  as  a matter  of 


course. 


OUR  TEACHERS  IN  SAILING  FLIGHT. 


29 


It  is  ever  with  a large  surplus  of  flying  capacity  that  nature 
has  equipped  her  subjects.  A stork  which  has  lost  some  of  its 
largest  pinions  does  not  for  that  reason  sail  less  gracefully  than 
its  comrades. 

Storks  are  not  particular  in  the  way  they  hold  their  pointed 
beaks  and  long  necks,  as  has  been  observed  already.  One 
after  the  other  sailed  over  our  heads ; one  held  itself  to  one 
side,  the  other  kept  to  the  other  side,  without  any  change  in 
their  flight.  Here  comes  another  one  very  slowly  against  the 
wind  ; just  as  it  stands  over  our  heads  it  bends  its  head  to  the  left 
to  take  a minute  survey  of  its  wings,  on  which  it  puts  its  head 
quite  to  one  side  and  begins  in  a most  leisurely  way  to  put  the 
feathers  on  its  left  wing  in  order  with  its  beak ; meanwhile  its 
graceful  sailing-flight  does  not  suffer  the  slightest  interruption. 
We  looked  at  one  another  surprised  by  this  sight,  as  if  we 
would  say,  “ That  is  beyond  everything ! For  thousands  of 
years  we  human  beings  have  racked  our  brains  to  unravel  the 
mysteries  of  flight,  and  we  feel  happy  when  we  drink  mere 
drops  from  the  Fount  of  Knowledge,  and  here  the  storks  seem 
to  run  riot  in  the  art  of  flying,  as  if  nothing  in  the  world  were 
easier.”  ^ 

Afterwards  I found  out  that  a stork,  putting  beak,  head,  and 
neck  back  quite  to  the  left,  certainly  changes  the  left  wing  a 
good  deal  more,  but  that,  in  this  position,  wherein  head  and  neck 
are  directly  in  front  of  the  arm  of  the  wing,  to  a certain  extent 
a broadening  of  the  left  wing  and  therefore  an  increase  in  the 
bearing  capacity  of  the  same  takes  place. 

One  might  therefore  not  be  at  all  surprised  if  the  balance  in 
soaring  be  not  disturbed.  The  young  storks,  which  are  known 
by  their  gray  legs,  betray  themselves  also  in  the  air  by  their 
less  sure  flight ; in  soaring  they  are  sometimes  thrown  here  and 
there  by  the  wind,  and  therefore  take  more  frequently  to  flap- 
ping their  -vCings  than  their  red-legged  parents,  which  understand 
in  a masterly  way  how  to  meet  every  gust  of  wind. 

1 Wir  Menschen  qualen  uns  seit  Jahrtausenden,  hinter  die  Rathsel  des  Fluges  zu  kom- 
men  und  sind  schon  froh,  wenn  wir  tropfenweise  aus  dem  Born  der  Erkenntniss  schdpfen 
kdnnen,  und  hier  wird  von  den  Stdrchen  in  einer  Weise  mit  dem  Flugverradgen  gewuchert, 
als  gabe  es  in  aller  Welt  nichts  Leichteres  als  das  Fliegen. 


30 


THE  AERONAUTICAL  ANNUAL, 


Whoever  observes  minutely  a stork,  which  is  proficient  in 
flying,  sailing  along  at  a moderate  height,  will  notice  a limited 
but  almost  uninterrupted  turning  and  moving  of  the  wings 
which  apparently  serve  to  exactly  meet  the  pressure  of  the 
wind.  Our  eyes  are  riveted  with  admiration  and  wonder  on 
each  of  these  birds  as  they  pass  along.  They  skim  and  sail  in 
the  air,  and  their  bodies,  weighing  four  to  five  kilograms,  appear 
to  be  borne  by  a magic  power.  Their  whole  behavior  indicates 
that  a flight  like  this  is  no  labor,  but  rather  akin  to  resting; 
their  tameness  lets  them  pass  close  to  us;  we  can  recognize  each 
feather  of  their  outspread  wings.  All  deception  as  to  the  real 
cause  of  sailing  flight  appears  excluded.  That  which  is  possi- 
ble to  these  storks  must  also  be  possible  to  any  other  similarly 
formed  flying  body. 

As  the  little  swallow,  which  just  now  sails  over  the  farm-yard 
through  the  broken  window  into  the  cow-shed,  understands  soar- 
ing on  the  same  principles  as  the  stork,  so  must,  on  the  other 
hand,  a larger  apparatus,  capable  of  bearing  up  a man,  be  able 
to  sail  on  the  wind,  if  it  be  of  the  right  shape. 

Of  course  such  an  apparatus  alone  cannot  equip  us  for  flying ; 
the  capability  of  using  it,  which  is  inborn  with  the  stork,  must  be 
gained  by  us  by  laborious  training,  but  even  in  this  we  can  trust 
ourselves  fully  to  our  long-legged  instructor.  It  shows  us  with 
what  facility  one  can  change  the  irregular  blowing  of  the  wind 
into  bearing-power,  provided  we  have  the  necessary  practice. 
When  the  stork  sails  over  the  roofs  of  the  houses  one  can  see 
how  it  applies  every  gust  in  the  air  to  its  advantage.  The  higher 
it  circles,  the  more  tranquil  and  certain  its  flight  becomes  in  pro- 
portion to  the  increasing  uniformity  of  the  wind. 

A particularly  fine  spectacle  is  a stork  remaining  for  a great 
length  of  time  floating  (remaining  stationary)  at  one  point  in 
the  air.  This  feat  also,  where  all  the  forces  are  equally 
balanced,  I saw  performed  by  older  storks  only.  These  mas- 
ters in  the  art  of  flying  understand  how  to  keep  their  position 
at  one  point  even  in  high  winds,  as  well  as  to  shoot  along  with 
high  velocity,  all  of  which  they  perform  by  careful  adjustment 
of  their  outspread  wings. 


OUR  TEACHERS  IN  SAILING  FLIGHT, 


31 


The  simplicity  of  the  instruments  with  which  nature  obtains 
these  wonderful  effects  in  flying  gives  us  hope  that  we  shall 
come  to  a satisfactory  solution  of  the  problem. 

Whoever  needs  incentive  to  labor  with  zeal  ought  to  look  up 
the  little  village  of  Vehlin  in  Ostprignitz  in  mid-summer,  when 
the  magnificent  birds  in  their  fine  black  and  white  garments  sail 
majestically  overhead,  and  are  seen  against  the  blue  of  heaven 
like  emblems  of  liberty. 


[From  Aero.  Ann.,  1897.] 


AT  RHINOW. 


[The  following  is  a translation  of  an  extract  from  an  article  by  Lilienthal  in 
Zeitschrift  fiir  Luftschiffahrt,  March,  1895.] 

Lilienthal  writes  thus  of  the  extreme  care  needed  in  making 
changes  in  an  air-sailing  machine : 

My  neglect  of  this  circumstance  I once  came  near  paying 
dearly  for.  The  winter  before  last  I constructed  several 
machines,  the  sustaining  surfaces  of  which  had  an  exact  parabolic 
profile  which  almost  coincided  with  the  arc  of  a circle.  The 
holding  point  for  the  hands  and  arms  I placed  in  such  a manner 
that  the  centre  of  gravity  of  the  body  was,  on  the  average, 
situated  one-tenth  of  the  width  of  the  wing  in  front  of  the  centre 
of  the  surface.  In  my  experiments  made  before  Easter  from 
the  still  higher  mountains  near  Rhinow,  I perceived  that  I had 
to  bear  with  the  upper  part  of  my  body  a good  deal  towards  the 
back  to  prevent  my  shooting  forward  in  the  air  with  the  appa- 
ratus. During  a gliding  flight  taken  from  a great  height  this 
was  the  cause  of  my  coming  into  a position  with  my  arms  out- 
stretched, in  which  the  centre  of  gravity  lay  too  much  to  the 
back ; at  the  same  time  I was  unable  — owing  to  fatigue  — to 
draw  the  upper  part  of  my  body  again  towards  the  front.  As  I 
was  then  sailing  at  the  height  of  about  65  feet  with  a velocity 
of  about  35  miles  per  hour,  the  apparatus,  overloaded  in  the  rear, 
rose  more  and  more,  and  finally  shot,  by  means  of  its  vis  viva, 
vertically  upwards.  I gripped  tight  hold,  seeing  nothing  but  the 
blue  sky  and  little  white  clouds  above  me,  and  so  awaited  the 
moment  when  the  apparatus  would  capsize  backwards,  possibly 
ending  my  sailing  attempts  forever.  Suddenly,  however,  the 
apparatus  stopped  in  its  ascent,  and,  going  backward  again  in  a 
downward  direction,  described  a short  circle  and  steered  with 
the  rear  part  again  upwards,  owing  to  the  horizontal  tail  which 
had  an  upward  slant ; then  the  machine  turned  bottom  upwards 

(32) 


AT  RHINOW. 


33 


and  rushed  with  me  vertically  towards  the  earth  from  a height 
of  about  65  feet.  With  my  senses  quite  clear,  my  arms  and  my 
head  forward,  still  holding  the  apparatus  firmly  with  my  hands, 
I fell  towards  a greensward ; a shock,  a crash,  and  I lay  with 
the  apparatus  on  the  ground. 

A flesh  wound  at  the  left  side  of  the  head,  caused  by  my 
striking  the  frame  of  the  apparatus,  and  a spraining  of  the  left 
hand,  were  the  only  bad  effects  of  this  accident.  The  apparatus 
was,  strange  to  say,  quite  uninjured.  I myself,  as  well  as  my 
sailing  implements,  had  been  saved  by  means  of  the  elastic 
recoil-bar,  which,  as  good  luck  would  have  it,  I had  attached 
for  the  first  time  at  the  front  part  of  the  apparatus.  This 
recoil-bar,  made  of  willow  wood,  was  broken  to  splinters ; it  had 
penetrated  a foot  deep  into  the  earth,  so  that  it  could  only  be 
removed  with  difficulty.  I describe  this  accident  so  minutely 
because  it  is  probably  the  worst  which  could  happen  in  sailing 
flight ; I wish  to  say  that  this  is  not  the  accident  which  gained 
publicity  through  the  press,  and  which  was  the  cause  of  a cor- 
respondence from  all  countries.  The  only  outside  spectators 
of  this  fall  were  the  little  girls  and  boys  of  the  Stdllner  schools, 
who  had  had  vacation,  and  were  looking  on  with  their  teachers 
at  my  experiments  from  the  ridge  of  the  mountain. 

My  brother,  who  also  took  part  in  these  experiments  and  had 
been  able  to  get  a perfect  side-view  of  my  unsuccessful  flight, 
said  it  had  looked  as  if  a piece  of  paper  had  been  sailing  about 
in  the  air  at  random.  In  my  thousands  of  experiments  this  is 
the  only  fall  of  that  kind,  and  this  I could  have  avoided  if  I had 
been  more  careful. 

If  one  uses  the  necessary  precautions  when  making  the  experi- 
ments, any  great  danger  is,  strictly  speaking,  excluded.  The 
use  of  a recoil-bar  is,  of  course,  always  advisable. 

In  the  very  slight  accident  which  a reporter  who  hap- 
pened to  be  present  brought  into  the  papers  in  a greatly  exag- 
gerated and  incorrect  way,  the  elastic  impact  of  the  recoil-bar 
proved  to  be  excellent.  In  this  experiment  a change  in  the 
curve  of  the  surfaces  came  into  account.  I was  occupied  in 
testing  wings  of  the  strongest  possible  curves  to  make  compara- 


34 


THE  AERONAUTICAL  ANNUAL. 


tive  experiments  regarding  the  influence  of  the  amount  of  con- 
cavity on  the  bearing  capacity.  I had  already  taken  several 
successful  flights  with  an  apparatus  the  concavity  of  which  was 
a little  over  of  the  breadth  of  the  wing ; then  while  sailing,  the 
apparatus  was  pressed  down  in  front  by  a wind  from  above,  in 
the  middle  of  the  course  of  flight,  by  means  of  which  it  was  run 
to  the  ground. 

With  these  strongly  curved  profiles  the  danger  is,  that  the 
surface  being  strongly  inclined,  the  front  receives  some  pressure 
of  the  air  from  above  in  consequence  of  sudden  changes  in  the 
wind,  and  this  would,  of  course,  greatly  diminish  the  stability  of 
the  flight.  As  has  already  been  observed,  it  is  not  advisable  to 
extend  the  height  of  the  profile  beyond  yV  of  the  breadth  of 
the  wings,  in  spite  of  the  excellent  sustaining  qualities  which 
may  so  be  obtained. 

One  can  produce  very  safe  working  qualities  with  strong 
power  of  sustentation  with  a height  of  profile  between  and 
of  the  breadth  of  the  wing. 

As  a matter  of  course,  the  more  one  penetrates  into  the 
details  of  the  technics  of  flight  the  more  varied  the  points  of 
view  will  become.  This  is  the  case  even  with  simple  sailing 
flights  which  demand  only  a simple  sustaining  surface.  How 
much  more  this  will  be  the  case  in  dynamic  flight ! I have  had 
already  enough  impressions  as  to  that.  But  of  this  some  other 
time. 


[From  Aero.  Ann.,  1897.] 


THE  BEST  SHAPES  FOR  WINGS. 

By  Otto  Lilienthal. 


[Abridged  translation  from  Zeitsckrift  fur  Luftschiffakrt,  XIV.  Jahrgang, 

Heft  10.] 

The  results  which  we  reach  by  practical  flying  experiments 
will  depend  most  of  all  upon  the  shapes  which  we  give  to  the 
wings  used  in  experimenting. 

Therefore  there  is  probably  no  more  important  subject  in  the 
technics  of  flying  than  that  which  refers  to  wing  formation. 

The  primitive  idea  that  the  desired  effects  could  be  produced 
by  means  of  flat  wings  has  now  been  abandoned,  for  we  know 
that  the  curvature  of  birds’  wings  gives  extraordinary  advan- 
tages in  flying. 

The  experiments  on  the  resistance  of  air  to  curved  surfaces 
have  shown  that  even  very  slight  curvatures  of  the  wing-profile 
increase  considerably  the  sustaining  power,  and  thereby  dimin- 
ish the  amount  of  power  required  in  flight. 

The  wing  of  a bird  is  excellent  not  only  because  of  the  cur- 
vature of  its  cross-section,  but  the  rest  of  its  structure  and  forma- 
tion also  has  influence  upon  the  flight.  Therefore  the  outline 
of  the  wing  is  certainly  of  importance. 

It  is  probable  that  the  form  of  the  cross-section  of  the  wing 
and  flight-feathers  {^Schwungfedern')  has  a favorable  influence 
upon  the  flight. 

Experiments  have  not  yet  been  made  to  show  conclusively 
whether  or  not  the  feather  structure  of  a wing  endows  it  with 
a special  quality  whereby  the  sustaining  power  is  increased. 
With  investigators  this  has  been  a subject  of  conjecture. 
Therefore  it  is  questionable  {auch  fragile Jt)  whether  we  are 
wrong  if,  in  constructing  flying  apparatus,  we  keep  to  the  bat’s 
wing,  which  is  easier  to  construct. 

Bats  fly  much  better  than  is  generally  thought.  Two  early 

(35) 


36 


THE  AERONAUTICAL  ANNUAL. 


bats,  which  I saw  flying  this-  suiftmei*  in  broad  sunshine  and  in 
somewhat  windy  weather,  sailed  along  so  well  without  flapping 
their  wings  that  I thought,  at  first,  they  were  swallows.  Of 
course  on  evenings  when  there  is  no  wind,  the  bat  must  flutter 
continually.  The  early-flying  bat  is  also  called  evening-sailer 
(^Abendsegler)  which  indicates  that  its  sailing  flight  has  been 
marked. 

The  most  important  point  as  regards  the  form  of  the  wing 
will  always  be  the  curvature  of  its  profile.  If  we  examine  any 
bird’s  wing  we  find  that  the  enclosed  bones  cause  a decided 
thickening  at  the  forward  edge.  The  question  now  is.  What 
part  does  this  thickening  play  in  the  action  of  the  curved 
surface?  The  thickening  is  quite  considerable,  particularly  in 
birds  which  have  long,  narrow  wings.  An  albatross  in  my  pos- 
session has  a breadth  of  wing  i6  centimetres,  the  thickened  part 
of  which  measures  2 centimetres ; the  thickness  is  therefore 
^ of  the  breadth  of  the  wing.  As  the  albatross  is  one  of  the 
best  sailers,  we  can  scarcely  assume  that  the  comparatively 
great  thickness  of  the  wing  at  its  outer  edge  has  a detrimental 
effect  upon  the  bird’s  flight. 

For  a long  time  I have  assumed  that  the  thickening  which 
all  birds’  wings  have  at  the  front  edge  produces  a favorable 
effect  in  sailing  flight. 

By  means  of  free-sailing  models  I have  now  learned  that 
nature  makes  a virtue  of  necessity,  that  the  thickened  front 
edge  is  not  only  harmless,  but  in  sailing  flight  is. helpful  (^son- 
dern  den  Schwebe-ejfect  nicht  unerheblich  erhoht) . 

The  experiments  are  easily  tried.  It  is  only  necessary  to 
make  a number  of  models  of  equal  size  and  weight,  each  one 
having  a different  curve  in  its  sustaining  surfaces.  These 
models  I make  of  strong  drawing  paper,  the  size  of  the  sur- 
faces being  about  4 inches  in  width  by  20  inches  in  length.* 

The  experimenter  can  let  these  models  sail  from  any  tower 
or  roof  in  front  of  which  there  is  an  open  space.  Each  model 
must  be  made  to  glide  through  the  air  many  times  until  it 


^ Drawings  of  these  models  will  be  found  on  pp.  14  and  15.  Aeronautical  Annual,  No.  2. 


“ofiR  c mema 

THE  BEST  SHAPES  FOR  WINGS.  37 

reaches  the  ground.  Experiments  must  be  made  in  the  stillest 
possible  air. 

The  lengths  of  flights  are  all  noted  down,  and  from  a long 
series  of  experiments  the  arithmetical  mean  for  each  design 
is  computed.  The  models  having  the  best  profiles  will  make 
the  longest  flights.  In  this  way  a reliable  table  can  be  made 
which  will  show  the  relative  merits  of  the  profiles,  and  will  also 
show  quite  plainly  in  which  direction  the  most  useful  form  will 
have  to  be  developed. 

Until  now  I have  endeavored  to  find  out  the  best  proportions 
for  wings  by  constructing  different  kinds  of  sailing  apparatus. 
In  this  way,  of  course,  many  important  facts  have  been  ascer- 
tained. The  construction  of  full-sized  apparatus  requires  a 
great  deal  of  time  and  is  expensive,  therefore  we  must  welcome 
a method  which  permits  inquiry  into  the  forms  of  wings  in 
models  which  fly  automatically.  Besides  that,  it  is  not  every 
one’s  business  to  throw  himself  into  space  in  a sailing  appara- 
tus, although  he  who  would  succeed  in  practical  flying  can 
scarcely  avoid  this  way. 

Considering  the  fact  that  the  most  important  thing  is  to 
ascertain  what  are  the  best  qualities  of  the  natural  wing,  — 
which  is  in  every  respect  perfect,  — these  steadily  sailing  models 
offer  every  one  an  opportunity  of  engaging  in  experiments  of 
this  kind.  Further,  any  one  who  takes  up  this  kind  of  experi- 
ment will  find  great  pleasure  in  watching  the  manoeuvres  of  his 
small  flyers,  which  often  vie  with  the  best  sailers  among  birds. 
I can  therefore  recommend  this  occupation  not  only  for  the 
furthering  of  the  science  of  mechanical  flight,  but  also  because 
it  affords  a most  interesting  pastime. 

The  few  measurements  made  so  far  by  this  method  are  too 
incomplete  to  be  fit,  as  yet,  for  publication.  I am  preparing, 
however,  a systematic  series  of  experiments,  the  results  of 
which  will  be  stated  when  the  experiments  are  finished. 

Meanwhile,  I cherish  the  hope  that  this  paper  may  be  an 
incentive  to  others  to  make  similar  experiments,  so  that  we  may 
sooner  reach  the  desired  end. 

Note.  — This  is  a part  of  Lilienthal’s  unfinished  work,  which  it  is  to  be  hoped  will  be 
taken  up  by  many.  The  fact  that  he  thought  it  well  worth  doing  is  significant.  — Ed. 


[From  Aero.  Ann.,  1897.] 


OTTO  LILIENTHAL 

A MEMORIAL  ADDRESS  DELIVERED  BEFORE  THE 

DEUTSCHEN  VEREIN  ZUR  FOR  DERUNG  DER  LUFTSCHIFFAHRT, 
NO  VEMBER  26,  i8g6. 

By  Karl  Mullenhoff. 


[Translated  from  Zeitsckrift  ftir  Luftscktffakrt.'\ 

The  irreparable  loss  which  our  Society  has  sustained  in  the 
death  of  Otto  Lilienthal  is  still  fresh  in  our  memories.  We  all 
remember  distinctly  the  untiring  character  of  him  who  united 
the  definiteness  of  aim  which  characterizes  manhood  with  all 
the  ardor  and  enthusiasm  of  youth. 

For  a long  time,  more  than  ten  years  in  fact,  Lilienthal  was  a 
member  of  our  Society,  and  only  a few  of  our  oldest  members 
can  remember  the  whole  of  the  energy  which  he  devoted 
to  our  work.  This  is  why  I,  who  introduced  Lilienthal  into 
the  Society,  will  endeavor  to  show  what  his  membership  really 
meant;  all  the  more  so,  as  it  was  I especially  who  was  fortunate 
enough  during  the  many  years  of  mutual  intercourse  to  really 
know  the  depths  of  this  noble  character  and  to  learn  to  appre- 
ciate it.  During  this  long  period  I had  the  good  fortune  to  be 
initiated  into  all  the  phases  of  his  studies  of  the  problem  of 
manflight. 

Otto  Lilienthal  was  born  May  24th,  1848,  at  Anclam  in  Pom- 
erania. Up  to  his  sixteenth  year  he  went  to  the  Latin  High 
School  of  his  native  city;  in  1864  he  entered  the  Potsdam  Tech- 
nical School ; after  graduation  from  this  institution  in  1866  he 
began  the  study  of  civil  engineering  by  a one  year’s  practical 
course  in  Schwartzkopf  s machine  shops.  From  1867  to  1870 
he  was  a student  at  the  Berlin  Technical  Academy,  and  he  had 
just  been  graduated  from  that  academy  when,  in  the  summer  of 
1870,  the  beginning  of  the  Franco-Prussian  war  called  him  into 
the  service. 


(39) 


40 


THE  AERONAUTICAL  ANNUAL. 


He  served  as  volunteer  in  the  Fusileer  Infantry  Regiment 
of  the  Guards,  and  was  with  that  regiment  at  the  siege  of 
Paris.  After  the  campaign  was  over  he  took  a place  as  civil 
engineer  in  Weber’s  machine  shops  at  Berlin,  and  was  after- 
wards, from  1872  to  1880,  engaged  in  the  large  machine  shops 
of  C.  Hoppe,  of  Berlin. 

In  1880  he  started  a machine  factory  of  his  own,  and  suc- 
ceeded, in  the  course  of  time,  in  bringing  it  to  a flourishing  con- 
dition by  his  energy  and  inventive  powers. 

The  products  of  his  machine  shops  were  of  great  variety. 
One  of  his  inventions  was  the  construction  of  light  steam  motors 
with  serpentine  pipes.  He  also  made  a specialty  of  marine 
signals.  His  achievements  in  these  procured  for  him  the  silver 
State  medal.  The  fog-horn  which  could  be  heard  during  the 
time  of  the  Berlin  trade  exhibition  near  the  Imperial  ship  was 
constructed  and  exhibited  by  him. 

From  his  earliest  youth  he  had  been  much  interested  in  the 
subject  of  manflight,  and  as  early  as  1861,  being  only  thirteen 
years  of  age,  he  began  to  make  practical  flying  experiments, 
together  with  his  younger  brother  Gustavus.  The  first  wings 
made  by  the  two  brothers  consisted  of  light,  flaps  which  were 
fastened  to  the  arms ; with  these  they  attempted  running  down- 
hill. The  experiments  were  mostly  made  at  night  by  moon- 
light, the  young  flying  artists  being  naturally  afraid  of  the  teas- 
ing of  their  school-fellows. 

The  experiments  which  had  been  started  in  Anclam  were  con- 
tinued in  Potsdam.  The  two  brothers  constructed  wings  which 
were  fastened  to  the  back,  and  which  moved  up  and  down  by 
throwing  out  the  legs  as  in  swimming.  In  1867  and  1868  while 
in  college,  Lilienthal  constructed  a more  complicated  apparatus. 
In  these  experiments  also  his  brother  Gustavus  took  an  active 
part. 

The  experiments  interrupted  in  consequence  of  the  campaign 
were  taken  up  again  as  early  as  the  autumn  of  1871. 

Lilienthal  had  seen  that  the  negative  results  of  previous 
flying  experiments  could  be  traced  to  the  fact  that  it  had  been 
the  custom  to  attempt  the  solution  of  the  problem  of  birds’ 


Plate  Vn. 


OTTO  LILIENTHAL. 
Born  1848.  Died  1896. 


" For  thousands  of  years  we  human  beings  have  racked  our  brains  to  unravel  the  mysteries  of 
flight  and  we  feel  happy  when  we  drink  mere  drops  from  the  Fount  of  Knov'.ledge,  and  here  the 
storks  seem  to  run  riot  in  the  art  of  flying,  as  if  nothing  in  the  world  were  easier.” 


OTTO  LILIENTHAL, 


41 


flight  trusting  only  to  incomplete  and  even  sometimes  erro- 
neous observations ; or  else  to  undertake  the  task  of  deriving 
the  laws  of  the  mechanics  of  flight  purely  theoretically  without 
resorting  to  any  observations  at  all. 

Both  methods  would  naturally  lead  to  erroneous  results. 
Lilienthal  concluded  to  investigate  the  whole  subject  by  means 
of  exact  experiment,  examining  scrupulously  all  the  phenomena 
to  be  seen  in  the  flight  of  birds.  He  began  by  measuring  — by 
means  of  a long  series  of  systematic  measurements  — the 
amount  of  the  resistance  of  the  air  which  the  bird’s  wing  has 
to  overcome  when  in  motion. 

These  experiments  and  measurements  were  for  a long  period 
made  only  by  Otto  Lilienthal,  with  the  help  of  his  brother. 
They  showed  the  important  and  new  result,  that  the  curved 
wings,  which  nature,  as  we  know,  provides  exclusively  for  her 
subjects,  have  a much  more  effective  form  than  the  flat  sur- 
face hitherto  so  often  constructed  by  men. 

Besides  this,  Lilienthal  was  the  first  to  point  out  the  phenom- 
enon which  he  thought  was  the  probable  explanation  of  the 
action  of  birds  in  sailing  flight;  that  is,  the  existence  of  air- 
currents  with  upward  tendency. 

According  to  the  observations  made  by  Lilienthal  these  cur- 
rents form  on  the  average  an  angle  of  3^  degrees  with  the  line 
of  the  horizon. 

Otto  Lilienthal  described  the  results  of  his  numerous  experi- 
ments in  his  pamphlet  of  the  year  1889,  entitled  “ The  Flight  of 
Birds  as  a Basis  for  the  Art  of  Flying.” 

Shortly  afterwards  with  the  greatest  zeal  he  again  took  up  the 
practical  attempts  at  flying  which  he  had  begun  so  long  before. 
He  had  come  to  the  conclusion  that  he  could  scarcely  attain  the 
solution  of  the  problem  of  flight  in  his  study,  but  that  he  must 
take  the  knowledge  he  had  gained  by  observation  and  calculation 
out  into  the  open  air,  to  test  with  the  wind,  and  in  the  element 
for  which  it  was  made,  the  apparatus  constructed  according  to 
the  theories  he  had  developed.  Theorizing  alone  would  never 
bring  about  success.  Brooding  over  and  calculating  about 
it  would  not  bring  one  to  the  desired  goal.  One  must  draw 


42 


THE  AERONAUTICAL  ANNUAL. 


up  plans,  build  a machine,  and  then  experiment  with  it, 
Lilienthal  was  right  in  pointing  to  the  example  of  the  bicycle  to 
show  how  important  practical  experiments  are  in  contrast  to 
pure  theory.  Without  doubt,  our  ancestors  would  have  shaken 
their  heads  incredulously  over  the  problem  of  the  bicycle ; it 
was  first  solved  practically  and  now  has  come  the  theoretical 
solution.  Of  all  the  various  methods  of  flying  which  nature 
shows  us,  sailing  flight  seemed  the  most  worthy  of  imitation.  It 
allows,  as  observation  shows,  the  swiftest  and  most  uninter- 
rupted motion  forward  with  a minimum  of  physical  exertion. 
The  solving  of  the  mystery  of  this  sailing-flight  must  therefore 
be  the  most  important  task  of  the  flight  technician. 

The  apparatus  used  by  the  experimenter  in  resuming  his 
attempts  in  the  spring  of  1891  had  the  shape  of  birds’  wings 
when  spread  out.  The  cross-section  through  the  wing  lying 
in  the  plane  of  the  direction  of  flight  was  curved  parabolically ; 
the  surfaces  of  the  wings  comprised  in  the  beginning  10  square 
metres  ; they  decreased  gradually  on  account  of  various  changes 
and  repairs  to  8 square  m.etres.  [The  width  comprised  at  its 
greatest  7 m.  by  2 m.]  The  framework  of  the  wings  was 
formed  of  willow-wood ; the  covering  was  made  of  sheeting 
covered  with  wax.  The  weight  of  the  apparatus  was  about  18 
kilos. 

In  order  to  hold  the  apparatus  the  arms  are  placed  in  two 
cushioned  openings  in  the  frame,  the  hands  at  the  same  time 
grasping  two  corresponding  handles.  In  this  way  the  wings  are 
perfectly  under  control,  and  may  be  safely  leaned  on  in  the  air. 

At  first,  of  course,  the  flying  experiments  were  made  only 
from  a low  height  and  when  there  was  no  wind.  Lilienthal 
made  a spring-board  on  a large  lawn  in  his  garden  in  Lichte- 
felde  which  could  be  made  higher  by  degrees ; when  first 
experimenting  the  board  was  but  one  metre  high,  later  it  was 
raised  to  two  metres.  On  the  spring-board  he  could  take  a run 
of  eight  metres  in  length.  In  spite  of  the  jump  the  landing  on 
the  soft  earth  was  gentle,  so  that  a jump  like  this  could  be 
repeated  many  times  without  resulting  in  the  least  weariness 
or  danger. 


OTTO  LILIENTHAL. 


43 


On  having  practised  sufficiently  the  jumping  off  in  this 
manner  without  wind,  he  selected  another  practising  ground  be- 
tween Werder  and  Gross-Kreutz  where  several  mounds  of  larger 
size,  standing  alone,  made  the  experiments  possible.  Here  it 
was  found  at  once  that  in  these  experiments  particular  attention 
must  be  given  to  the  wind  then  blowing.  It  is  necessary  when 
floating  to  move  against  the  wind,  for  if  one  falls  away  from  the 
wind,  the  pressure  of  the  wind  is  felt,  and  the  experimenter  is 
not  able  to  resist  the  one-sided  effect.  A vertical  steering  sur- 
face therefore  had  to  be  put  on,  thus  enabling  the  apparatus  to 
go  against  the  wind. 

On  the  grounds  between  Werder  and  Gross-Kreutz  the  jump- 
ing was  done  very  frequently  from  greater  heights  and  with 
winds  of  different  force ; a great  deal  of  new  experience  was 
thus  obtained.  The  final  result  was,  that  jumps  of  20—25 
metres’  length  could  be  made  from  the  highest  jumping  point 
there,  from  a height  of  5 to  6 metres.  This  was  done  when 
there  was  no  wind  as  well  as  with  winds  of  different  force. 

The  difference  showed  itself  particularly  in  the  duration  of  the 
flight;  the  stronger  the  winds,  the  longer  the  journey  in  the  air. 
The  fact  that  landing  when  there  is  no  wind  is  often  a rather 
violent  affair  corresponds  to  what  has  been  said,  and  it  is 
therefore  necessary  to  raise  the  wings  a little  in  front  shortly 
before  landing,  in  order  to  mitigate  the  harshness  of  the  shock 
and  to  prevent  tilting  over.  This,  however,  refers  only  to  flight 
when  there  is  no  wind ; if  the  flight  is  against  the  wind,  the 
landing  on  the  ground  is  of  an  absolutely  gentle  nature. 

The  practising  places  not  offering  enough  space  to  cover 
longer  distances  from  greater  heights,  another  spot,  suitable 
for  continuing  the  experiments,  had  to  be  chosen  in  the  follow- 
ing year,  1892. 

Such  a place  was  found  between  Steglitz  and  Siidende.  The 
slopes  here  have  a height  of  about  10  metres. 

The  experiments  were  made  with  an  enlarged  apparatus  with 
a surface  of  16  square  metres  and  24  kilos’  weight,  at  a velocity 
of  the  wind  up  to  7 metres.  He  could  take  a start  up  to  the 
jumping  place,  thereby  obtaining  a relative  velocity  of  the  air 


44 


THE  AERONAUTICAL  ANNUAL. 


of  lo  metres  per  second.  Under  these  circumstances  the  first 
part  of  the  sailing  flight  was  almost  horizontal ; in  its  further 
course  the  line  of  flight  sank  considerably  and  declined  rather 
suddenly  at  the  end,  as  the  wind  loses  a part  of  its  force  in  the 
lower  strata.  In  the  most  favorable  case  the  length  of  the  jump 
would  be  equal  to  8 times  the  height  of  the  jumping  place  above 
the  landing  point. 

The  surroundings  of  Berlin  having  a great  dearth  of  good 
places  for  trying  such  flying  experiments,  Lilienthal  constructed 
at  Maihdhe  near  Steglitz  a flying  station  of  his  own  in  the  spring 
of  1893.  A small  declivity  on  this  hill  was  arranged  for  a sta- 
tion for  sailing  flights.  A tower-like  shed  was  built,  from  the 
roof  of  which  the  flights  were  made,  and  which  thus  afforded  a 
jumping  place  of  10  metres’  height.  The  interior  of  the  shed 
was  used  for  storing  the  apparatus.  The  roof,  which  for  the 
sake  of  a more  secure  start  was  covered  with  turf,  sloped  down, 
as  did  the  declivity  round  the  shed,  towards  south-west,  west, 
and  north-west.  The  apparatus  showed  a change  as  compared 
with  that  of  previous  years  ; it  could  be  folded  together,  like  the 
wings  of  the  bat.  It  could,  in  consequence  of  this  arrangement, 
be  removed  more  easily  and  stored  at  almost  any  place. 

It  was  only  seldom,  however,  that  the  wind  was  favorable  on 
the  Maihdhe,  and  it  was  thus  most  important  for  the  energetic 
continuing  of  the  flying  experiments  that  — in  1893 — Lilien- 
thal succeeded  in  finding  grounds  which  were  suitable  for  his  pur- 
poses in  every  respect.  These  are  on  the  Rhinow  mountains 
near  Rathenow.  Out  of  surrounding  flat  plough-lands  there 
rises  a chain  of  hills  covered  only  with  grass  and  heath,  of  up 
to  60  or  even  — as  at  the  Gollenberg  — up  to  80  metres’  height 
above  the  plain.  The  hills  offer  on  every  side  descents,  at  an 
angle  of  from  10  to  20  degrees;  and  it  is  possible  here  to  select 
a suitable  position  in  whatever  direction  the  winds  make  de- 
sirable, in  order  to  glide  above  them  through  the  air.  The 
grounds  really  appear  to  be  made  for  such  flying  experiments. 
The  wind  does  not  produce  such  gusts  as  at  the  flying  tower 
at  Steglitz,  where  one  would  always  receive  an  irregular  gust 
of  wind  from  below,  when  passing  the  edge  of  the  jumping 


OTTO  LILIENTHAL. 


45 


place.  Often  enough  this  gust  threatened  to  be  fatal.  Besides, 
this  uniform  acclivity  permitted  landing  anywhere. 

The  wings  which  were  used  showed  some  changes  as  com- 
pared with  those  used  previously.  Their  weight  is  20  kilos, 
the  complete  weight  just  100  kilos,  the  width  from  tip  to  tip 
7 metres,  the  greatest  breadth  2^  metres,  the  complete  surface 
14  square  metres,  a size  which  appears  to  be  fully  sufficient. 

The  wings  are  lowered  when  the  experimenter  runs  down- 
hill against  the  wind ; at  the  proper  moment  he  raises  the  sup- 
porting surfaces  a little,  so  that  they  are  about  horizontal ; 
then  while  poising  in  the  air  he  endeavors  by  suitably  chang- 
ing the  point  of  gravity  to  give  to  the  apparatus  such  a posi- 
tion that  it  shoots  quickly  forward  while  lowering  itself  as 
little  as  possible.  After  a short  time  a great  progress  in  the  safe 
management  of  the  apparatus  could  be  observed.  Very  often 
sailing  flights  of  200  to  300  metre  length  were  made  from  a 
height  of  30  metres ; a great  additional  progress  consisted  in 
the  fact  that  he  succeeded  in  directing  the  course  of  flight  to 
the  right  and  left.  Changing  of  the  point  of  gravity  is  effected 
by  stretching  the  legs  in  one  or  the  other  direction ; even  a 
slight  change  of  the  centre  of  gravity  brings  about  at  once  a 
decline  of  the  supporting  surfaces  towards  the  direction  desired, 
the  pressure  of  the  air  also  increasing  on  this  side.  The  direc- 
tion of  the  course  of  flight  then  deviates  to  that  side.  Several 
times  during  the  experiments  the  deviation  from  the  straight 
line  of  flight  was  carried  so  far  that  Lilienthal  would  at  times 
return  to  the  starting  place. 

A place  which  was  very  well  suited  for  his  experiments,  and 
much  more  conveniently  situated,  was  procured  by  Lilienthal  in 
the  spring  of  1894,  in  Gross-Lichterfelde  near  Berlin;  he  caused 
a conic  hill  to  be  thrown  up,  which,  having  a height  of  15 
metres  and  at  the  basis  a diameter  of  70  metres,  should  admit 
of  flying  experiments  in  whatever  direction  the  wind  blew. 

On  this  place  he  tried  with  good  success  his  new  flying 
apparatus,  consisting  of  two  surfaces  arranged  one  above  the 
other. 


46 


THE  AERONAUTICAL  ANNUAL. 


He  had  come  to  the  point  already  that  the  experiments  re- 
garding sailing  flight  could  be  considered  as  being  completed, 
and  he  proposed  to  take  up  the  second  task,  viz.,  the  imitating 
of  the  rowing  flight  of  birds.  A light  machine,  weighing  in 
all  only  40  kilos  and  supplying  2 J horse-power  for  a short  time 
(4  minutes),  was  constructed  and  tested  several  times.  Lilien- 
thal  was  therefore  certainly  justifled  in  his  words,  when  he  de- 
clared in  a lecture  given  in  July,  ’96,  in  the  Berlin  trade  exhibi- 
tion buildings,  that  he  had  strong  hopes  of  being  able  to  further 
still  more  the  development  of  the  flying  sport ; but  an  accident 
put  an  untimely  end  to  his  endeavors  on  the  9th  of  August. 

He  had  made,  on  that  fatal  day,  a very  extensive  sailing  flight 
on  the  Rhinow  mountains,  and  thereby  the  special  steering  of 
the  movable  horizontal  tail  had  proved  to  be  very  satisfactory; 
he  then  wanted  to  undertake  a second  flight  of  as  long  a dura- 
tion as  possible,  and  wanted  to  define  the  duration  of  the  flight. 

As  a rule,  such  flights  would  last  from  12  to  15  seconds. 
He  gave  the  timing-piece  to  his  assistant.  According  to  the 
statement  of  the  latter,  the  flight  was  — up  to  half  of  the  course 
of  flight  — almost  horizontal ; then  the  apparatus  had  suddenly 
tilted  over  in  front,  and  had  shot  down  rapidly  from  a height  of 
15  metres,  being  completely  tilted  over  on  the  ground.  The 
daring  sportsman  was  dragged  from  the  debris.  His  spine  being 
broken,  he  died  twenty-four  hours  later. 

At  present  one  cannot  foresee  what  development  may  be  in 
store  for  the  principles  laid  down  by  Lilienthal  in  the  art  of  fly- 
ing: one  thing  however  is  certain,  that  not  one  of  the  numerous 
explorers  and  experimenters  who  have  busied  themselves  with 
the  problem  of  flying  has  done  so  much  as  Lilienthal  to  bring 
the  difficult  problem  nearer  its  solution.  It  has  therefore  been 
justly  emphasized,  in  the  many  accounts  and  debates  which 
Lilienthal’s  experiments  have  called  forth  over  the  whole  world, 
that  he  possessed  three  qualities  in  happiest  union : He  was 
first  a thorough  mathematician  and  physicist,  and  had  given  im- 
portant contributions  to  the  theory  of  flight  by  reason  of  his 
untiring  observations  and  measurements  of  the  resistance  of 
the  air  to  curved  surfaces.  Second,  being  a clever  constructor. 


OTTO  LILIENTHAL, 


47 


and  especially  as  mechanical  engineer,  he  was  able  to  build  the 
apparatus  himself  as  he  thought  best  fitted  for  imitating  the 
flight  of  birds.  Third,  he  possessed  great  daring  and  physical 
dexterity,  so  that  he  was  in  himself  fitted  for  making  experi- 
ments in  flying. 

Therefore  his  memory  will  be  faithfully  cherished  by  all  those 
who  have  decided  to  labor  on  in  the  field  of  work  which  he 
made  his  own. 


[From  Aero.  Ann.,  1896.] 


OCTAVE  CHANUTE. 


(WITH  PORTRAIT.) 

Octave  Chanute,  ex-President  of  the  American  Society  of 
Civil  Engineers,  was  born  in  Paris,  France,  Feb.  18,  1832,  and 
came  to  the  United  States  in  the  latter  part  of  1838.  He  re- 
ceived his  education  chiefly  in  New  York  City,  and  began  the 
practice  of  his  profession  as  a civil  engineer  in  1849,  the 
construction  of  the  Hudson  River  Railroad,  under  JOHN  B. 
Jervis,  Chief  Engineer. 

He  was  gradually  promoted  as  the  work  progressed  over  the 
several  divisions  of  the  road,  and  when  he  left  the  service  of 
that  company,  in  1853,  he  was  Division  Engineer  at  Albany,  in 
charge  of  the  completion  of  terminal  facilities  and  maintenance 
of  way  between  Hudson  and  Albany. 

In  1853  he  went  to  Illinois  with  H.  A.  Gardner,  previously 
Chief  Engineer  of  the  Hudson  River  Railroad,  and  was  there  en- 
gaged in  building  what  is  now  a part  of  the  Chicago  & Alton 
Railroad,  between  Joliet  and  Bloomington,  in  Illinois,  hlr. 
Chanute  remained  upon  this  work  until  1854,  when  he  was 
made  Chief  Engineer  of  the  eastern  portion  of  what  is  now  the 
Toledo,  Peoria,  & Warsaw  Railroad.  He  built  this  road  from 
Peoria  to  the  Indiana  State  line,  a distance  of  about  1 12  miles, 
and  remained  in  charge  of  maintenance  of  way  until  1861.  In 
the  latter  year  he  became  Division  Engineer,  with  similar  duties, 
on  the  Pittsburg,  Fort  Wayne,  & Chicago  Railroad,  between 
Chicago  and  Fort  Wayne. 

In  1 862  he  was  for  six  months  Chief  Engineer  of  Maintenance 
of  Way  of  the  Western  Division  of  the  Ohio  & Mississippi  Rail- 
road, from  St.  Louis  to  Vincennes.  In  1863  he  became  Chief 
Engineer  of  Maintenance  of  Way  and  Construction  of  the  re- 

(4S) 


GBOVER  c.  bergooli. 


OCTAVE  CHANUTE. 


OCTAVE  CHANUTE. 


49 


organized  Chicago  & Alton  Railroad,  and  remained  upon  that 
line  until  1867. 

During  this  connection,  having  been  invited  to  submit  a 
design  for  the  proposed  Union  Stock  Yards  of  Chicago,  his  plan 
was  selected  in  competition  with  a number  of  others  and  he 
built  these  yards  as  Chief  Engineer.  He  was  also  awarded  a 
premium  for  a competitive  design  for  a bridge  across  the 
Missouri  River  at  St.  Charles,  Missouri.  In  1867  Mr.  Chanute 
went  to  Kansas  City,  Mo.,  as  Chief  Engineer  of  the  bridge  across 
the  Missouri  River  at  that  point.  This  was  the  pioneer  bridge 
across  the  Missouri  River,  and  as  the  river  pilots  and  riparian 
dwellers  had  given  this  stream  a bad  reputation,  the  successful 
completion  of  this  bridge  across  it  in  1868  attracted  great  atten- 
tion and  interest. 

Meanwhile  the  building  of  railroads  had  begun  in  Kansas, 
and  while  yet  occupied  in  the  completion  of  the  bridge  Mr. 
Chanute  was  placed  in  charge  as  Chief  Engineer,  first  of  the 
construction  of  the  Kansas  City,  Fort  Scott,  & Gulf  Railroad, 
from  Kansas  City  to  the  north  line  of  the  Indian  Territory,  160 
miles ; next  of  a parallel  line  in  the  same  interest,  then  known 
as  the  Leavenworth,  Lawrence,  & Galveston  Railroad,  from 
Lawrence,  Kansas,  to  the  Indian  Territory;  next  of  a connect- 
ing line  between  the  two,  known  as  the  Kansas  City  & Santa  Fe 
Railroad,  and  lastly  of  the  Atchison  & Nebraska  Railroad  from 
Atchison  northward. 

While  simultaneously  in  charge  of  the  construction  of  these 
four  railroads,  he  also  designed  and  built  the  Union  Stock  Yards 
at  Kansas  City;  and  in  1871,  as  the  work  drew  to  a close,  he 
became  general  Superintendent  of  the  Leavenworth,  Lawrence, 
& Galveston  Railroad. 

In  1873  he  was  offered  and  accepted  the  position  of  Chief 
Engineer  of  the  Erie  Railway,  which,  having  changed  its  man- 
agement, was  planning  to  make  extensive  improvements. 
These  were  to  consist  of  doubling  the  tracks  and  narrowing  the 
gauge  ; building  an  extension  to  Chicago  and  another  to  Boston, 
involving  the  Poughkeepsie  bridge  since  built  in  another 


50 


THE  AERONAUTICAL  ANNUAL. 


interest ; building  sundry  branches,  and  improving  the  property 
generally  at  an  estimated  outlay  of  some  fifty  millions  of 
dollars,  which  it  was  expected  to  obtain  in  England. 

The  panic  of  1873  and  the  subsequent  financial  depression 
prevented  the  full  carrying  out  of  this  programme.  Mr. 
Chanute,  however,  remained  upon  the  Erie  Railway  10  years, 
during  which  time  much  of  the  line  was  double-tracked  upon 
improved  grades,  the  gauge  reduced  to  the  standard  by  laying 
down  a third  rail,  and  the  facilities  of  the  line  largely  improved. 
In  1875  he  was  made  Assistant  General  Superintendent,  and  in 
1876  was  placed  temporarily  in  charge  of  the  motive  power  and 
rolling  stock,  in  addition  to  his  duties  as  Chief  Engineer.  This 
gave  him  an  opportunity  of  readjusting  the  locomotives  as  well 
as  the  grades,  so  that  the  through  freight  train,  which  averaged 
18  cars  when  he  first  became  connected  with  the  line,  had  grown 
to  35  cars  when  he  closed  his  connection  with  the  road  in  1883, 
when  he  removed  from  New  York  to  Kansas  City,  in  order  to 
look  after  his  personal  interests,  and  to  open  an  office  as  Con- 
sulting Engineer. 

In  this  latter  capacity  he  took  charge  of  the  construction  of 
the  iron  bridges  during  the  building  of  the  Chicago,  Burlington, 
& Northern  Railroad  between  Chicago  and  St.  Paul  in  1885, 
and  of  those  of  the  extension  of  the  Atchison,  Topeka,  & Santa 
Fe  Railroad,  from  Kansas  City  to  Chicago,  in  1887  and  1888; 
the  latter  involving,  besides  a number  of  minor  streams,  the 
Missouri  River  bridge  at  Sibley,  and  the  Mississippi  River  bridge 
at  Fort  Madison. 

In  1889  Mr.  Chanute  removed  his  office  to  Chicago,  where 
he  is  now  principally  engaged  in  promoting  the  preserv^ation  of 
timber  against  decay  by  chemical  methods ; he  being  of  the 
opinion  that  the  time  has  now  fully  arrived  when  large  econ- 
omies are  to  be  attained  in  this  country  by  employing  the 
methods  which  are  in  current  use  abroad. 

Mr.  Chanute  became  a member  of  the  American  Society  of 
Civil  Engineers,  Feb.  19,  i868,  and  has  contributed  a goodly 
number  of  papers  to  its  Transactions.  Among  these  may  be 


OCTAVE  CHANUTE. 


mentioned,  “The  Elements  of  Cost  of  Railroad  Freight  Traffic,” 
“ Rapid  Transit  and  Terminal  Freight  Facilities,”  “ The  Preser- 
vation of  Timber,”  the  latter  two  being  reports  by  committees 
of  which  he  was  chairman ; “ Engineering  Progress  in  the 
United  States,”  “Repairs  of  Masonry,”  and  “Uniformity  in 
Railroad  Rolling  Stock,”  besides  some  contributions  to  various 
other  societies. 

The  foregoing  biographical  sketch  is  reprinted  from  Engi- 
neering News,  N.Y.,  1891.  Since  it  appeared,  Mr.  Chanute  has 
rendered  to  the  cause  of  aeronautical  science  a service  of  the 
greatest  value.  He  has  written  one  of  the  most  important  books  ^ 
on  flying  machines  which  has  ever  appeared ; he  took  an  active 
part  in  the  proceedings  of  the  International  Conference  on 
Aerial  Navigation  held  in  Chicago  at  the  time  of  the  World’s 
Fair ; he  has  also  given  most  generous  pecuniary  aid  to  experi- 
menters in  need  of  money. 

His  high  attainments  as  an  engineer  enable  him  to  estimate 
with  rare  precision  the  value  of  the  experiments  made  by  others 
and  to  show  investigators  just  what  bearing  their  individual 
work  has  upon  the  world’s  work.  — Ed. 

[1910.  Mr.  Chanute  still  lives  in  Chicago  and  rejoices  to 
have  seen  his  anticipations  realized.] 


Progress  in  Flying  Machines,”  N.Y.,  1894. 


[From  Aero.  Ann.,  1897.] 


RECENT  EXPERIMENTS  IN  GLIDING  FLIGHT. 

By  O.  Chantjte. 


Having  for  a number  of  years  studied  the  physical  princi- 
ples underlying  flight,  and  having  passed  in  review  the  experi- 
ments of  others  in  a series  of  articles  which  eventually  swelled 
into  a book,^  I ultimately  reached  the  conclusion  that  the  con- 
tingent compassing  of  artificial  flight  by  man  involved  the 
study  of  at  least  ten  separate  problems,  or  the  devising  of 
means  for  observing  and  mastering  the  conditions  enumerated 
as  follows : 

1.  The  resistance  and  supporting  power  of  air. 

2.  The  motor,  its  character  and  its  energy. 

3.  The  instrument  for  obtaining  propulsion. 

4.  The  form  and  kind  of  the  apparatus. 

5.  The  extent  of  the  sustaining  surfaces. 

6.  The  material  and  texture  of  the  apparatus. 

7.  The  maintenance  of  the  equilibrium. 

8.  The  guidance  in  any  desired  direction. 

9.  The  starting  up  under  all  conditions. 

10.  The  alighting  safely  anywhere. 

It  is  probable  that  some  of  these  problems  can  be  solved  in 
more  ways  than  one,  and  these  solutions  must  then  be  har- 
moniously combined  in  a design  which  shall  deal  with  the 
general  problem  as  a whole,  before  the  best  possible  result  is 
attained. 

1 further  reached  the  conclusion  that  the  seventh  problem, 
the  maintenance  of  the  equilibrium  under  all  circumstances,  was 
by  far  the  most  important,  and  the  first  which  should  be  solved  ; 
that  until  automatic  stability,  at  all  angles  of  flight  and  condi- 
tions of  wind,  was  evolved,  and  safety  thereby  secured,  it 


1 “ Progress  in  the  Flying  Machines,”  M.  N.  Forney,  N.Y.,  Editor,  1894. 

(52) 


RECENT  EXPERIMENTS  IN  GLIDING  FLIGHT. 


53 


would  be  premature  to  seek  to  apply  a motor  or  a propelling 
instrument  in  a full-sized  machine,  as  these  additions  would 
introduce  complications  which  might  be  avoided  at  the  begin- 
ning, 

I seriously  doubted,  at  first,  whether  automatic  stability 
could  be  secured  with  an  artificial  machine ; whether  such 
combinations  could  be  devised,  for  an  inanimate  apparatus, 
as  to  perform  the  complicated  functions  of  the  life  and  instinct 
of  the  birds,  who  probably  preserve  their  balance  through 
almost  unconscious  reflex  action  of  their  nerves  and  muscles. 
Observation,  however,  indicated  that  this  might  be  automatic, 
requiring  no  thought  under  ordinary  conditions,  and  the  final 
conclusion  was  reached  that  it  might  be  possible  to  evolve  an 
artificial  apparatus  which  should  afford  automatic  stability  and 
safety  most  of  the  time ; that  the  variations  of  the  wind  were 
the  great  difficulties  to  be  encountered,  that  they  must  be  met 
and  overcome,  and  that  perhaps  they  might  be  utilized  in 
obtaining  propulsion  and  support,  as  is  daily  done  by  the 
soaring  birds. 

I therefore  published  an  article  in  the  “ Engineering  Maga- 
zine ” for  April,  1896,  in  which  I advised  those  seeking  a 
solution  of  the  problem  of  flight  to  turn  their  attention  to  ex- 
periments in  soaring  flight,  with  full-sized  apparatus  carrying  a 
man,  as  the  quickest,  cheapest,  and  surest  way  of  ascertaining 
the  exact  conditions  which  must  be  met  in  practical  flight. 

This  mode  of  procedure  doubtless  involves  a certain  amount 
of  personal  danger  of  accident.  It  might  be  pointed  out  that 
the  advice  is  easy  to  give,  but  hazardous  to  follow,  and  so  I 
further  determined  to  try  such  experiments  myself,  so  far  as 
my  limited  personal  means  would  allow. 

For  this  purpose  I secured  the  services  of  Mr.  A.  M.  Her- 
ring, who  had  tried  some  experiments  of  his  own.  He  rebuilt 
for  me  his  Lilicnthal  apparatus,  with  which  he  had  made 
some  gliding  flights  in  1894,  and  he  also  built  another  full- 
sized  gliding  apparatus  after  a design  of  my  own. 

These  were  completed  in  June,  1896,  and  on  the  22d  of  that 
month  we,  a party  of  four  persons,  went  into  camp  in  the  desert 


54 


THE  AERONAUTICAL  ANNUAL. 


sand  hills  on  the  south  shore  of  Lake  Michigan,  just  north  of 
the  station  of  Miller,  Ind.,  30  miles  east  of  Chicago. 

These  sand  hills  have  been  piled  up  by  the  wind  blowing  the 
sand  from  the  beach.  They  gradually  increase  in  altitude,  from 
a point  about  10  miles  east  of  Chicago  to  the  vicinity  of  St. 
Joseph,  Mich.,  on  the  east  shore  of  the  lake,  where  they  attain 
a height  of  200  or  300  feet.  They  occupy  a strip  two  to  five 
miles  wide  around  the  south  and  south-eastern  turns  of  Lake 
Michigan,  and  are  bleak,  bare,  and  deserted,  being  entirely  inca- 
pable of  cultivation.  North  of  Miller,  Ind.,  these  hills  rise  about 
70  feet  above  the  lake.  They  are  of  soft  yellow  sand,  almost 
bare  of  vegetation,  and  face  in  every  direction  of  the  compass, 
so  that  almost  all  directions  of  wind  can  be  utilized  in  gliding 
experiments. 

The  method  of  carrying  on  these  adventures  is  for  the  oper- 
ator to  place  himself  within  and  under  the  apparatus,  which 
should,  preferably,  be  light  enough  to  be  easily  carried  on  the 
shoulders  or  by  the  hands,  and  to  face  the  wind  on  a hillside. 
The  operator  should  in  no  wise  be  attached  to  the  machine. 
He  may  be  suspended  by  his  arms,  or  sit  upon  a seat,  or  stand 
on  a dependent  running  board,  but  he  must  be  able  to  disen- 
gage himself  instantly  from  the  machine  should  anything  go 
wrong,  and  be  able  to  come  down  upon  his  legs  in  landing. 

Facing  dead  into  the  wind,  and  keeping  the  front  edge  of 
the  supporting  surfaces  depressed,  so  that  the  wind  shall  blow 
upon  their  backs  and  press  them  downward,  the  operator  first 
adjusts  his  apparatus  and  himself  to  the  veering  wind.  He  has 
to  struggle  to  obtain  a poise,  and  in  a moment  of  relative  steadi- 
ness he  runs  forward  a few  steps  as  fast  as  he  may,  and  launches 
himself  upon  the  breeze,  by  raising  up  the  front  edge  of  the  sus- 
taining surfaces,  so  as  to  receive  the  wind  from  beneath  at  a very 
small  angle  (2  to  4 degrees)  of  incidence.  If  the  surfaces  and 
wind  be  adequate,  he  finds  himself  thoroughly  sustained,  and  then 
sails  forward  on  a descending  or  undulating  course,  under  the 
combined  effects  of  gravity  and  of  the  opposing  wind.  By 
shifting  either  his  body  or  his  wings,  or  both,  he  can  direct  his 
descent,  either  sideways  or  up  or  down,  within  certain  limits ; 


Plate  IX. 


Fig.  I.  — GLIDING  MACH'NE. 


Fig.  2. 


RECENT  EXPERIMENTS  IN  GLIDING  FLIGHT. 


55 


he  can  cause  the  apparatus  to  sweep  upward  so  as  to  clear  an  ob- 
stacle, and  he  is  not  infrequently  lifted  up  several  feet  by  a swell- 
ing of  the  wind.  The  course  of  the  glide  eventually  brings  the 
apparatus  within  a few  feet  of  the  ground  (6  to  lo  feet),  when 
the  operator,  by  throwing  his  weight  backward,  or  his  wings 
forward  if  they  be  movable,  causes  the  front  of  the  supporting 
surfaces  to  tilt  up  to  a greater  angle  of  incidence,  thus  increas- 
ing the  wind  resistance,  slowing  the  forward  motion,  and  enabling 
him,  by  a slight  oscillation,  to  drop  to  the  ground  as  gently  as 
if  he  had  fallen  only  one  or  two  feet. 

These  manoeuvres  require  considerable  quickness  and  dex- 
terity, yet  they  are  easily  learned  in  a few  days,  the  principal  rule 
to  be  learned  being  that  the  movements  to  be  bodily  made  are 
the  reverse  of  those  instinctive  motions  which  would  occur  to 
catch  one’s  self  from  falling  if  walking  on  the  ground.  In  point 
of  fact,  we  found  that  a week’s  practice  sufficed  for  a young, 
active  man  to  become  reasonably  expert  in  these  manoeuvres, 
and  hundreds  of  glides  were  made  with  the  several  machines, 
experimented  in  1896  under  variable  conditions  of  wind,  with- 
out the  slightest  personal  accident. 

As  before  stated,  we  went  into  camp  on  the  22d  of  June, 
1896.  The  party  consisted  of  Mr.  A.  M.  Herring,  already 
mentioned,  Mr.  W.  Avery,  an  electrician  and  carpenter,  Mr.  Will- 
iam Paul  Butusov,  a former  sailor,  and  myself.  The  tent  was 
large  enough  to  shelter  the  machines,  but  we  learned  in  a few 
days  that  this  precaution  was  unnecessary,  and  that  they  could 
be  safely  left  exposed  to  the  wind,  outside,  by  tying  them  down 
to  pegs  or  to  bushes,  or  even  by  loading  them  down  with  sand. 
There  was  a fishing  station  of  two  houses  within  a mile  of  the 
tent,  from  which  outside  aid  might  have  been  obtained  in  the 
improbable  case  of  an  accident.  Miller  Station  was  two  miles 
inland,  and,  having  come  through  that  station  with  our  sus- 
picious baggage,  we  soon  had  more  visitors  than  was  altogether 
pleasant  in  preliminary  experiments. 

The  Lilienthal  machine  was  first  set  up.  It  is  shown,  poised 
for  a flight,  in  Plate  IX.,  Fig.  i . The  wings  were  20  feet  from 
tip  to  tip,  7 feet  6 inches  in  maximum  breadth,  and  measured 


56 


THE  AERONAUTICAL  ANNUAL. 


1 68  square  feet  in  surface,  with  a weight  of  36  pounds.  Mr.. 
Herring,  who  had  used  it  before,  took  the  lead  in  gliding  with  it. 

It  was  realized  from  the  first  that  the  machine  was  difficult  to 
handle  and  to  poise  in  the  wind.  The  variable  puffs  pelted  the 
apparatus ; they  occasionally  lifted  one  wing  more  than  the 
other,  or  rocked  the  machine  fore  and  aft,  so  that  a struggle 
was  necessary  before  a poise  could  be  obtained.  Once  under 
way  the  same  action  continued,  and  the  operator  was  compelled 
to  shift  his  weight  constantly,  like  a tight-rope  dancer  without  a 
pole,  in  order  to  bring  the  centre  of  gravity  directly  under  the 
centre  of  pressure  and  to  avoid  being  upset.  This,  in  fact,  is 
the  principle  of  the  Lilienthal  apparatus.  The  equilibrium 
depends  upon  the  constant  readjustment  of  the  weight,  so  as 
to  coincide  with  the  variable  position  of  the  centre  of  pressure 
due  to  the  shifting  direction  and  force  of  the  wind.  Lilienthal, 
who  evolved  this  machine,  so  superior  to  any  that  had  preceded 
it,  was  an  expert  in  its  use.  He  made  thousands  of  flights 
without  serious  accident ; but  it  is  due  to  those  who  may  desire 
to  repeat  such  experiments  to  state  here  plainly  that  we  found 
it  cranky  and  uncertain  in  its  action  and  requiring  great  prac- 
tice. If  strongly  built  it  was  not,  however,  nearly  so  hazardous 
to  life  and  limb  as  the  above  statement  would  seem  to  imply. 
The  radiating  ribs  forming  the  frame  of  the  wings  extend  down- 
ward about  as  low  as  the  waist  of  the  operator  when  in  flight, 
and  whenever  an  awkward  landing  is  made,  by  reason  of  the 
apparatus  tilting  to  one  side  or  the  other,  the  ribs  on  that  side 
are  the  first  to  strike  the  ground.  Acting  as  springs,  breaking 
or  not  as  the  case  might  be,  they  save  the  operator  from  bodily 
harm  even  in  a descent  of  20  feet.  These  breakages  were 
easily  repaired  by  wiring  on  wooden  splints  to  the  ribs,  so  that 
practice  could  be  resumed  in  a few  minutes. 

About  100  glides  were  made  with  this  machine,  the  longest 
being  1 16  feet,  and  the  heights  started  from  were  20  to  30  feet 
in  winds  of  12  to  17  miles  per  hour.  Mr.  Avery  proved  an 
apt  pupil,  and  in  the  course  of  a week  learned  to  manage  the 
machine  nearly  as  well  as  Mr.  Herring.  Mr.  Butusov  did  not 
do  so  well  and  was  upset,  but  not  harmed.  I did  not  venture 


RECENT  EXPERIMENTS  IN  GLIDING  FLIGHT. 


57 


myself,  feeling  that  I was  no  longer  young  and  active  enough  to 
perform  such  acrobatic  exercises  without  breaking  the  appa- 
ratus. After  it  had  been  broken,  mended,  tried  again,  and 
overhauled  a goodly  number  of  times,  it  was  finally  decided, 
on  the  29th  of  June,  to  discard  it,  and  it  was  accordingly 
broken  up. 

This  decision  was  most  unfortunately  justified  on  the  loth  of 
the  succeeding  August,  when  Herr  Lilienthal  met  his  death 
while  experimenting  with  a machine  based  on  the  same  prin- 
ciple, but  with  two  superposed  sets  of  wings.  This  deplorable 
accident  removed  the  man  who  has  hitherto  done  most  to  show 
that  human  flight  is  probably  possible,  who  was  the  first  in 
modern  times  to  endeavor  to  imitate  the  soaring  birds  with 
full-sized  apparatus,  and  who  was  so  well  equipped  in  every 
way  that  he  probably  would  have  accomplished  final  success 
if  he  had  lived. 

Having  discarded  the  Lilienthal  machine,  we  next  turned 
our  attention  to  the  apparatus  after  my  own  design.  This  was 
based  upon  just  the  reverse  of  the  principle  involved  in  the 
Lilienthal  apparatus.^  Instead  of  the  man  moving  about,  to 
bring  the  centre  of  gravity  under  the  centre  of  pressure,  it  was 
intended  that  the  wings  should  move  automatically  so  as  to 
bring  the  movable  centre  of  pressure  back  over  the  centre  of 
gravity,  which  latter  should  remain  fixed.  That  is  to  say,  that 
the  wings  should  move  instead  of  the  man. 

The  apparatus  consisted  in  12  wings,  each  6 feet  long  by  3 
feet  wide,  measuring  14^  square  feet  in  area,  each  pivoted  at  its 
root  to  a central  frame,  so  that  it  could  move  fore  and  aft,  this 
action  being  restrained  by  springs.  The  main  frame  was  so 
constructed  that  the  wings  could  be  grouped  in  various  ways, 
so  as  to  ascertain  the  best  arrangement  for  maximum  support 
and  for  counterbalancing  the  effects  of  wind  gusts,  if  possible. 
The  total  wing  surface  was  177  square  feet,  and  the  weight  was 
37  pounds.  Fig.  2,  Plate  IX.,  shows  the  first  grouping  tested, 
which  was  found  at  once  to  be  reasonably  steady,  but  deficient 
in  lifting  power.  It  was  recognized  that  the  wings  interfered 


1 To  establish  priority  of  invention  a patent  has  been  applied  for. 


58 


Cf  'i  In*  r> 

Air*! 

THE  AERONAUTICAL  ANNUAL. 


with  each  other’s  efficiency;  that  the  wind  was  deflected 
downward  by  the  front  wings,  so  that  the  middle  and  rear 
wings  did  not  afford  the  same  sustaining  power  as  at  the  front. 
After  making  a few  glides  with  this  arrangement,  a series  of 
changes  was  tried  to  ascertain  what  was  the  best  grouping  and 
the  best  distance  between  the  wings  in  order  to  obtain  the 
maximum  lift  and  the  greatest  steadiness.  The  paths  of  the 
wind  currents  in  each  arrangement  of  the  wings  were  indicated 
by  liberating  bits  of  down  in  front  of  the  machine,  and,  under 
their  guidance,  six  permutations  were  made,  each  of  which  was 
found  to  produce  an  improvement  in  actual  gliding  flight  over 
its  predecessors. 

The  final  arrangement  to  which  this  series  of  experiments 
led  is  shown  on  page  75.  Five  of  the  pairs  of  wings  had 
gradually  accumulated  at  the  front,  and  the  operator  was 
directly  under  them,  while  the  sixth  pair  of  wings  formed  a tail 
at  the  rear,  and  being  mounted  so  as  to  flex  upward  behind  in 
flight,  preserved  the  fore  and  aft  balance.  It  was  at  once 
demonstrated  that  this  apparatus  was  steady,  safe,  and  manage- 
able in  winds  up  to  20  miles  an  hour.  With  it  about  100  glides 
were  made.  The  longest  of  these  was  82  feet,  in  a descend- 
ing course  of  about  i in  4,  against  a wind  of  13  miles  an 
hour;  the  object  constantly  in  view  being  not  to  make  long 
glides,  but  to  study  the  equilibrium  of  the  machine  and  the 
principles  which  should  govern  in  developing  it  further.  These 
were  found  to  be  that  the  supporting  surfaces  should  be  con- 
centrated at  the  front  and  the  man  placed  directly  under  them ; 
that  the  lowest  wings  should  be  at  least  2^  feet  above  the 
ground ; that  they  should  be  about  two-thirds  of  their  breadth 
apart  vertically,  and  not  less  than  their  breadth  apart  horizon- 
tally, being  set  so  as  to  present  an  angle  of  incidence  of  3 to  7 
degrees  above  the  horizon  when  in  flight,  and  that  the  wings 
should  be  pivoted  so  as  to  move  very  easily,  the  friction  upon 
this  first  set  of  pivots  having  been  found  entirely  too  great  to 
permit  the  wings  adjusting  themselves  easily  to  the  variations 
of  the  wind,  and  the  man  having  had  to  move  his  body. 

Having  ascertained  these  facts,  the  experiments  were  termi- 


GROVER  C.  BERCfOil 

Plate  X. 


CHANUTE'S  1896  GLIDING  MACHINE  IN  FLIGHT. 


RECENT  EXPERIMENTS  IN  GLIDING  FLIGHT. 


59 


nated  on  the  4th  of  July,  and  the  equipment  was  sent  back  to 
Chicago  in  order  to  rebuild  the  machine. 

It  may  safely  be  asserted  that  more  was  learned  concerning 
the  practical  requirements  of  flight  during  the  two  weeks  occu- 
pied by  these  experiments  than  I had  gathered  during  many 
previous  years  of  study  of  the  principles  involved,  and  of 
experiments  with  models.  The  latter  are  instructive,  it  is  true, 
but  they  do  not  reveal  all  the  causes  for  the  vicissitudes  which 
occur  in  the  wind.  They  do  not  explain  why  models  seldom 
pursue  exactly  the  same  course,  why  they  swerve  to  the  right 
or  left,  why  they  oscillate,  or  why  they  upset.  When  a man  is 
riding  on  a machine,  however,  and  his  safety  depends  upon  the 
observance  of  all  the  conditions,  he  keenly  heeds  what  is 
happening  to  him,  and  he  gets  entirely  new  and  more  accurate 
conceptions  of  the  character  of  the  element  which  he  is  seeking 
to  master. 

The  fact  which  most  strongly  impressed  itself  upon  us  was 
the  inconstancy  of  the  wind.  It  is  incessantly  changing  in 
direction  and  in  strength.  This  fact  is  not  new,  it  has  been 
well  shown  experimentally  by  Mr.  A.  F.  Zahm,  by  Professor 
Langley,  and  probably  by  others,  but  its  effects  upon  a man- 
ridden  machine  must  be  seen  and  felt  to  realize  that  this  is  the 
great  obstacle  to  be  overcome  in  compassing  artificial  flight. 
It  cannot  be  avoided,  it  cannot  be  temporized  with,  and  it  must 
be  coped  with  and  conquered  before  we  can  hope  to  have  a 
practical  flying-machine. 

One  remarkable  feature  of  the  wind,  however,  struck  us  as 
hitherto  unknown,  or  at  least  unmentioned.  The  wind  gusts 
seem  to  come  in  as  rollhig  waves,  rotating  at  a higher  speed  than 
the  general  forward  movement.  The  buffetings  which  the 
apparatus  received  from  the  wind,  while  the  operator  was  en- 
deavoring to  steady  it,  preparatory  to  a flight,  seemed  to  indi- 
cate that  he  was  struggling  with  a rotary  billow  which  produced 
the  fluctuations.  Professor  Langley  has  termed  these  fluctua, 
tions  “ the  internal  work  of  the  wind,”  and  it  is  quite  conceivable 
that  they  should  be  produced  by  a revolving  motion,  striking 
the  surfaces  with  velocities  varying  with  the  distance  from  the 


6o 


THE  AERONAUTICAL  ANNUAL. 


centre  of  rotation,  and  producing  all  the  pulsations  which  have 
been  revealed  by  the  instrumental  measurements. 

Mr.  Herring  first  called  my  attention  to  this  feature  of  the 
wind,  and  I have  ever  since  been  wondering  how  I could,  for  so 
many  years,  have  been  watching  smoke  curling  away  from 
chimneys,  steam  convolving  from  trains,  or  dust  and  leaves 
whirling  in  wind  gusts,  without  realizing  that  the  elastic  tenuity 
of  air  must  perforce  produce  rotary  motions  much  more  active 
than  those  which  occur  in  water. 

This  observation,  if  confirmed  by  further  investigation,  prom- 
ises to  give  us  a better  understanding  of  the  forces  to  be  mas- 
tered. There  are  indications  that  there  is  a certain  synchronism 
about  these  air  waves,  and  that  arrangements  can  be  devised, 
not  only  to  encounter  them,  but  to  avail  of  them  in  securing 
propulsion  and  automatic  stability. 

Be  this  as  it  may,  we  returned  to  Chicago  much  encouraged 
by  the  result  of  these  preliminary  experiments,  with  much 
clearer  ideas  as  to  the  difficulties  to  be  surmounted,  and  with 
good  hopes  that  by  reconstructing  the  machine  we  could 
obtain  still  better  performances. 

The  original  twelve-winged  machine  was  reconstructed  by 
pivoting  the  wings  upon  ball-bearings  placed  at  the  top  and 
bottom  of  wooden  uprights  fastened  to  the  main  frame.  The 
wings  at  the  front  were  reduced  to  ten  in  number,  in  order  to 
space  them  further  apart  without  increasing  their  total  height, 
but  one  pair  was  soon  taken  off,  and  the  required  supporting 
surface  was  restored  by  placing  a concave  aeroplane  over  the 
top  of  the  wings.  Two  pairs  of  wings,  superposed,  were  placed 
at  the  rear,  but  one  pair  was  taken  off  after  the  first  few  trials, 
and  the  apparatus,  provided  with  a rear  keel  or  rudder,  assumed 
the  shape  shown  in  Plate  XI.,  Fig.  i.  The  total  supporting  sur- 
face at  the  front  was  then  143.5  square  feet,  the  wings  at  the 
back  measured  29.5  square  feet,  and  the  weight  was  33^ 
pounds.  The  ball-bearings  are  at  the  level  of  the  lower  and  of 
the  third  pair  of  wings  from  the  bottom  in  the  figure,  and  each 
set  of  moving  wings,  four  in  number,  is  connected  rigidly  by 
vertical  wooden  rods  and  diagonal  wire  ties  so  as  to  move 


Plaie  XI. 


Fig.  2.  — CHANUTE’S  TWO-SURFACE  GLIDING  MACHINE. 


RECENT  EXPERIMENTS  IN  GLIDING  FLIGHT.  6 1 

together.  Elastic  rubber  springs  at  front  and  rear  connect  them 
with  the  frame  and  restrain  the  movements  produced  by  the 
fluctuations  of  the  wind  and  relative  speed.  The  detailed  con- 
struction of  the  apparatus  is  shown  on  Plate  XII.  It  had  been 
originally  intended  to  erect  the  machine  with  five  pairs  of 
superposed  wings  at  the  front,  and  they  were  in  fact  put  on,  but 
the  first  few  trials  in  the  wind  showed  that  the  height  and 
leverage  were  too  great  for  easy  control,  and  the  top  pair  was 
accordingly  taken  off. 

There  was  built  simultaneously  another  full-sized  machine, 
based  upon  a different  principle.  Instead  of  having  pivoted 
wings,  this  consisted  of  three  superposed  concave  surfaces, 
stretching  i6  feet  across  the  line  of  motion,  by  a breadth  of  4 
feet  3 inches,  these  surfaces  measuring  an  aggregate  of  19 1 
square  feet.  The  lower  surface  was  cut  away  at  the  centre  to 
admit  the  body  of  the  operator.  The  machine  was  provided 
with  a combined  horizontal  and  vertical  rudder,  and  its  total 
weight  was  31  pounds.  The  first  few  trials  developed  the  fact 
that  the  sustaining  power  was  in  excess,  and  that  the  bottom 
surface  was  too  near  the  ground.  It  was  removed,  leaving  the 
apparatus  in  the  condition  shown  on  Plate  XL,  Fig.  2.  The 
sustaining  surfaces  and  the  rudder  were  connected  by  an  auto- 
matic device,  designed  by  Mr.  Herring,  for  the  purpose  of 
securing  stability.  The  curvature  of  the  wings  (versed  sine) 
was  about  one-tenth  of  the  chord.  Estimates  were  made  in 
advance  of  head  resistance  due  to  the  framing  and  to  the 
drift  of  this  machine.  It  was  computed  that  it  required  a rela- 
tive speed  of  22  miles  an  hour  and  an  angle  of  incidence  of 
3 degrees  for  support,  and  that  its  angle  of  gliding  descent 
would  be  10  degrees,  or  i in  5.6,  which  computations  were 
fully  verified  in  the  experiments,  as  will  be  seen  hereafter. 

Still  a third  full-sized  machine  was  constructed  at  my  expense 
at  the  same  time.  This  was  designed  by  Mr.  William  Paul 
Butusov,  who  has  already  been  mentioned  as  being  present  at 
the  preliminary  trials  in  June,  and  who  stated  that  he  had  already 
tested  with  success  a similar  construction  some  seven  years 
previously.  This  closely  resembled  the  apparatus  experimented 


62 


THE  AERONAUTICAL  ANNUAL. 


by  Le  Bris  in  1855  and  1867.  It  consisted  in  a boat-like  frame 
of  ribs  and  stanchions,  which  might  be  covered  with  stout  oil- 
cloth and  thus  transformed  into  a boat.  Above  this  were  four 
longitudinal  keels  of  balloon  cloth,  stretched  on  a frame,  each  8 
feet  long  and  3 feet  deep.  The  central  space  was  left  open, 
but  the  two  side  spaces  were  roofed  over.  This  occupied  8 feet 
in  width,  and  immediately  above  were  placed  the  wings,  each 
16  feet  long,  by  a maximum  width  of  7 feet,  tapering  to  the  tips. 
The  total  spread  was,  therefore,  40  feet  from  tip  to  tip,  and  above 
this  again  a square  aeroplane  or  kite  was  placed,  hung  on  trunn- 
ions at  its  centre,  so  that  its  angle  of  incidence  might  be  varied 
at  will  by  lines  carried  to  the  hands  of  the  operator.  The  latter 
stood  upright  in  the  boat  on  a running  board  8 feet  long,  and 
might  therefore  shift  his  weight  to  that  extent  by  walking  for- 
ward or  backward,  and  he  might  also  shift  it  about  3 feet  side- 
ways by  leaning  to  one  side  or  the  other.  The  whole  arrange- 
ment is  shown  in  Plate  XIII.,  Fig.  i,  except  the  rudder  and  tail, 
which  are  partly  hidden  by  the  man,  and  which  are  moved  by 
light  lines  passing  over  pulleys  and  carried  to  his  hands.  In 
addition  to  this  a pair  of  parallel  bars  (curtain-poles)  were 
fastened  to  the  frame,  to  which  the  man  might  cling  or  brace 
himself. 

When  finally  completed  the  apparatus  spread  266  square 
feet  of  sustaining  surface  and  weighed  160  pounds.  The  various 
parts  (wings,  keel-roofs,  top  aeroplane,  and  tail)  were  then 
tested  by  suspending  them  inverted,  and  loading  them  with  sand 
to  the  maximum  load  they  might  be  called  upon  to  carry,  and 
as  some  of  them  showed  signs  of  crippling,  or  did  cripple,  they 
were  strengthened  with  additional  material  until  they  were  safe 
to  stand  the  strains.  This  brought  the  total  weight  up  to  190 
pounds. 

These  three  machines  being  ready,  we  again  went  to  the 
sand  hills  on  the  20th  of  August,  1896.  Having  on  the  previous 
occasion  found  the  vicinity  of  Miller  too  accessible  to  the 
public,  we  went,  this  time,  five  miles  further  down  the  beach, 
where  the  hills  were  higher,  the  solitude  greater,  and  the  path 
more  obscure  to  the  railroad,  which  it  reached  at  a sand-pit 


Plate  XU. 


Multiple-win&  Gliding  Machine  .Invented  by  O.ChanuteX.E. 


" £S6' 


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RECENT  EXPERIMENTS  IN  GLIDING  FLIGHT. 


63 


station  consisting  of  a single  house,  and  called  Dune  Park. 
The  distance  from  our  camp  was  about  two  miles,  through  a 
series  of  swamps,  woods,  and  hills,  so  that  intending  visitors 
not  infrequently  got  lost. 

We  went  from  Chicago  by  a sailing  vessel  in  order  to  avoid 
arousing  gossip  at  the  railroad  station,  and  in  the  afternoon  of 
August  2 1st  we  got  the  material  unloaded  and  the  tent 
pitched  at  the  experimental  hill.  We  hoped  to  begin  setting 
up  the  machines  on  the  morrow. 

Unfortunately,  that  very  night  a fearful  storm  and  whirling 
wind  came  up  from  the  south-west  at  3 A.M.  It  blew  the  tent 
to  ribbons,  blew  away  and  wrecked  such  wings  as  were  not 
boxed,  while  all  of  the  party  and  the  provisions  were  drenched, 
the  camp  equipage  being  moreover  scattered  and  damaged.^ 
It  became  necessary  to  send  at  once  to  Chicago  for  another 
tent,  which  arrived  at  Dune  Park  by  express  in  the  afternoon 
of  the  twenty-second,  but  this  disclosed  our  presence  to  the 
people  at  the  sand  pit,  and  some  ten  days  later  brought  down 
the  newspaper  reporters  to  see  what  we  were  about. 

Our  party  consisted  of  five  persons,  Mr.  Herring,  Mr.  Avery, 
Mr.  Butusov,  already  mentioned,  Dr.  Ricketts,  — a young  surgeon 
who  found  that  function  such  an  entire  sinecure  that  he  could 
only  exhibit  to  us  his  talents  in  cooking, — and  myself.  In  ad- 
dition to  this  there  was,  for  a time,  a carpenter  to  erect  the  tres- 
tle work  from  which  to  launch  the  Butusov  machine.  The  hill 
selected  faced  the  north  and  rose  100  feet  above  the  lake,  there 
being  an  intervening  beach  of  about  350  feet  between  its  base 
and  the  water.  It  was  of  soft  yellow  sand  with  many  bare 
slopes,  but  with  occasional  clumps  of  trees  and  bushes.  To  the 
south  it  sloped  to  a bare  wilderness  of  sand. 

The  first  machine  which  was  repaired  and  set  up  after  the  tor- 
nado was  the  aerocurve,  with  three  superposed  fixed  surfaces 
and  automatic  tail  attachment.  It  was  first  tested  on  the  29th 
of  August,  with  tentative  glides  from  a height  of  1 5 to  20  feet 
above  the  bottom  of  the  hill,  but  it  was  found  to  rock  so  that 
the  lower  surface  struck  the  ground,  hard  to  manage,  and  to  lift 


1 The  frying-pan  was  blown  200  yards  away. 


64 


THE  AERONAUTICAL  ANNUAL. 


more  than  required.  The  lower  aerocurve  was  therefore  taken 
off,  thus  reducing  the  sustaining  surface  to  135  square  feet,  and 
the  weight  to  23  pounds.  This  was  thereafter  found  ample  to 
sustain  an  aggregate  weight  of  178  pounds  (23  pounds  of  ma- 
chine and  155  pounds  of  operator),  and  all  the  subsequent  ex- 
periments were  made  with  this  arrangement.  During  the  next 
14  days  scores  and  scores  of  glides  were  made  with  this  machine, 
whenever  the  wind  served.  It  was  found  steady,  easy  to  handle 
before  starting,  and  under  good  control  when  under  way,  — a 
motion  of  the  operator’s  body  of  not  over  2 inches  proving  as 
effective  as  a motion  of  5 or  more  inches  in  the  Lilienthal  ma- 
chine. It  was  experimented  in  all  sorts  of  winds,  from  10  to  31 
miles  an  hour,  the  latter  being  believed  to  be  a higher  wind 
than  any  gliding  machine  had  been  tried  in  theretofore,  and  yet 
the  equilibrium  was  not  compromised,  the  machine  gliding 
steadily  at  speeds  of  about  17  miles  per  hour  with  reference  to 
the  ground,  and  of  about  20  to  40  miles  an  hour  with  reference 
to  the  air,  or  relative  wind.  On  one  occasion  a relative  speed 
of  52  miles  an  hour  was  acquired  in  a descent.  Some  of  the 
best  glides  made  were  as  follows: 


Operator. 

Length  in 
feet. 

Time  in 
seconds. 

Angle  of 
descent. 

Height 
fallen » feet. 

Speed,  feet 
per  second. 

Descent  of 

Avery 

199 

8. 

10=' 

34-6 

24.9 

I in  5.75 

Herring 

234 

00 

74“ 

304 

26.9 

I “ 7.69 

253 

1040 

46. 

I “ 5.50 

239 

I 1° 

46.3 

I “ 5.24 

220 

Q. 

24.4 

235 

10.3 

22.8 

Avery 

256 

10.2 

8° 

25.5 

25.1 

I in  7.18 

Herring 

359 

14. 

10° 

62.1 

25.6 

I “ 5-75 

One  of  these  flights  is  shown  by  Fig.  2,  Plate  XIII. 

The  varying  flatness  of  the  angle  of  descent  was  undoubtedly 
due  to  the  varying  strength  of  the  wind,  and  also  to  its  ascend- 


Plate  XII I 


Fig.  I. 


Fig.  2.— A GOOD  START. 


.•c:  .5 


’ j 


RECENT  EXPERIMENTS  IN  GLIDING  FLIGHT. 


65 


ing  trends  as  it  struck  the  slope  of  the  hill.  The  latter  were 
exhibited  by  liberating  bits  of  down  at  the  foot  of  the  hill, 
whence  they  would  ascend  parallel  with  the  surface  and  pass  over 
the  top  to  the  plain  beyond.  On  many  occasions  the  machine 
and  man  were  raised  higher  than  the  starting  point  by  increasing 
wind  velocity,  but  this  action  was  found  to  be  much  too  irregu- 
lar to  be  availed  of  as  a source  of  power. 

It  was  found  that  by  moving  the  operator’s  body  backward 
or  forward,  an  undulatory  course  could  be  imparted  to  the  appa- 
ratus. It  could  be  made  to  rise  several  feet  to  clear  an  obsta- 
cle, or  the  flight  might  be  prolonged,  when  approaching  the 
ground,  by  causing  the  machine  to  rise  somewhat  steeply  and 
then  continuing  the  glide  at  a flatter  angle.  It  was  very  interest- 
ing to  see  the  aviator  on  the  hillside  adjust  his  machine  and  him- 
self to  the  veering  wind,  then,  when  poised,  take  a few  running 
steps  forward,  sometimes  but  one  step,  and  raising  slightly  the 
front  of  his  apparatus,  sail  off  at  once  horizontally  against  the 
wind ; to  see  him  pass  with  steady  motion  and  ample  sup- 
port 40  or  50  feet  above  the  observer,  and  then,  having  struck 
the  zone  of  comparative  calm  produced  by  eddies  from  the  hill, 
gradually  descend  to  land  on  the  beach  several  hundred  feet 
away. 

A few  hidden  defects  were  gradually  evolved,  such  as  lack  of 
adjustment  in  the  automatic  device,  and  occasional  swerving 
out  of  the  course  in  sudden  gusts  of  wind ; but  safe  landings 
were  made  in  every  case,  by  simply  throwing  the  body  back 
and  causing  the  front  edge  of  the  aerocurve  to  rise  so  as  to 
diminish  the  speed ; and  the  machine  was  not  once  broken. 
It  was  kept  out  of  doors  moored  to  pegs  driven  in  the  sand, 
and  was  injured  by  storms  on  but  three  occasions.  It  was  con- 
cluded, however;  that  a permanent  machine  of  this  kind  should 
be  arranged  to  fold  up  (as  this  was  not)  so  as  to  admit  of 
carrying  it  about  and  of  sheltering  it  from  the  weather. 

The  movable  winged  machine  (12  wings)  was  not  set  up  till 
the  4th  of  September,  1896.  Upon  being  tested,  it  was  found  at 
once  that  a mistake  had  been  made  in  not  providing  entirely 
new  wings  for  it.  The  old  wings  were  so  racked,  twisted,  and 


66 


THE  AERONAUTICAL  ANNUAL. 


distorted  by  their  prior  service  that  they  did  not  lift  alike,  and 
that  it  was  difficult  to  poise  the  machine  and  to  balance  it  in 
the  wind.  Nothing  is  so  important  in  such  experiments  as  to 
keep  the  sustaining  surfaces  in  perfect  shape  and  to  prevent 
any  racking  when  under  strains.  This  is  inculcated  to  us  by 
the  birds,  who  are  constantly  “ pluming  ” themselves  when  on  the 
perch.  They  pass  each  flying  feather  through  their  beaks,  repair 
those  barbs  which  have  become  separated,  rearrange  the  lap  of 
the  feathers,  and  beat  their  wings  up  and  down  to  limber  up  the 
muscles.  I have  reason  to  believe  that  it  was  in  consequence 
of  the  failure  to  keep  his  apparatus  in  constant  rigid  good  order 
that  Herr  Lilienthal  so  unhappily  lost  his  life.  A correspond- 
ent in  Germany,  who  had  witnessed  his  exercises  two  weeks 
before  the  fatal  fall,  wrote  me  that  he  had  found  that  in  the 
particular  machine  with  which  the  accident  occurred  “ the  con- 
nections of  the  wings  and  of  the  steering  arrangements  were 
very  bad  and  unreliable,”  that  he  had  remonstrated  with  Herr 
Lilienthal  very  seriously,  and  the  latter  had  promised  that  he 
would  put  the  apparatus  in  order,  but,  with  that  contempt 
of  danger  which  long  familiarity  and  thousands  of  success- 
ful flights  is  sure  to  create,  it  is  much  to  be  feared  that  he 
did  not  attend  to  it  immediately,  especially  as  he  was  about  to 
discard  that  particular  machine  for  a new  one  from  which  he 
expected  great  results. 

It  was  also  found  that  in  spacing  the  wings  of  the  twelve- 
winged machine  further  apart,  it  had  been  made  too  high.  The 
top  was  10  feet  6 inches  above  the  ground,  and  the  leverage  of 
the  wind  made  it  difficult  for  the  operator  to  control  the 
machine.  The  top  pair  of  wings  was  accordingly  taken  off, 
and  the  experiments  thereafter  made  with  the  apparatus  as  cut 
down.  In  this  shape  it  proved  steady  and  manageable,  the 
flights  being  over  twice  as  long,  with  the  same  fall  as  with  the 
original  machine  in  June.  The  following  are  some  of  the  glides 
made  on  the  nth  of  September  against  a wind  of  22.3  miles 
per  hour; 


RECENT  EXPERIMENTS  IN  GLIDING  FLIGHT. 


67 


Operator. 

Length  in 
feet. 

Time  in 
seconds. 

Speed,  feet 
per  second. 

Remarks. 

Herring 

148 

7- 

21. 1 

Angle  not 

measured. 

Avery 

174 

7.6 

22.9 

« i( 

(C 

Herring 

166 

7-5 

22.1 

(i  « 

(( 

Avery 

183 

7-9 

23.1 

t<  t< 

(6 

Herring 

172 

7.8 

22. 

((  « 

“ 

The  angles  were  approximately  10  or  ii  degrees,  or  i in  5. 


This  machine  had  been  provided  with  a swinging  seat,  con- 
sisting of  network  with  a narrow  board  at  its  front,  and  with  a 
pair  of  swinging  bars  and  stirrups  against  which  the  legs  could 
be  braced,  so  as  to  move  the  wings  fore  and  aft  by  means  of 
light  lines  running  through  pulleys.  The  heights  started  from 
being  only  30  to  35  feet  above  the  base  of  the  hill,  and  the 
glides  being  accordingly  very  brief,  these  attachments  could 
not  be  brought  into  action,  but  their  efficacy  was  tested  by 
suspending  the  apparatus  between  two  trees  and  facing  the 
wind  with  a man  in  the  seat.  It  was  found,  as  was  expected, 
that  by  thrusting  the  wings  forward  the  machine  was  tossed  up, 
and  vice  versa  that  by  thrusting  one  wing  forward  the  machine 
turned  towards  the  opposite  side,  and  that  these  would  be 
effective  ways  of  directing  the  apparatus  when  under  flight, 
either  up  or  down,  or  in  a circling  sweep.  The  automatic 
regulation,  however,  did  not  work  as  well  as  was  hoped,  per- 
haps in  consequence  of  inaccurate  adjustment  of  the  springs. 
The  man  still  had  to  move  about  one  inch  to  preserve  the 
equilibrium  when  under  way.  The  machine  made  steady  flights 
and  easy  landings,  and  was  not  once  broken  in  action.  It  is 
certainly  considered  safer  and  more  manageable  than  the  Lilien- 
thal  apparatus  which  we  tested.  No  photographs  were  taken 
of  this  machine  in  flight,  as  it  was  not  tested  nearly  so  often  as 
would  have  been  desirable,  and  whenever  it  was,  something 
always  interfered  to  prevent  getting  the  camera. 


68 


THE  AERONAUTICAL  ANNUAL. 


It  must  be  confessed  that  the  results  with  this  apparatus  were 
rather  disappointing,  and  yet  the  principle  is  believed  to  be 
sound.  As  the  variations  of  the  wind  are  constantly  changing 
the  position  of  the  centre  of  pressure,  it  is  necessary  that  either 
the  wings  or  the  weight  shall  move,  or  that  the  angle  of  inci- 
dence relative  to  the  air  shall  be  absolutely  maintained  in  order 
to  keep  the  centre  of  pressure  and  the  centre  of  gravity  upon 
the  same  vertical  line.  These  are  the  two  principles  which  are 
involved  in  the  two  machines  which  have  herein  been  described. 
Which  of  the  two  shall  hereafter  prove  to  be  most  effective  in 
practical  use,  or  whether  the  two  can  be  combined,  cannot  be 
determined  at  present,  but  it  is  my  judgment  that  one  or  two 
more  seasons  should  be  devoted  to  perfecting  the  automatic 
equilibrium,  to  eliminating  hidden  defects,  and  to  adjusting  the 
strength  of  the  springs  and  moving  parts,  before  it  will  be  pru- 
dent to  apply  a motor,  or  to  try  to  imitate  the  soaring  of  the 
sailing  birds. 

Towards  the  last  we  gathered  such  confidence  in  the  safety  of 
the  machines  that  we  allowed  anybody  to  try  them  who  wanted  to. 
A number  of  amateurs  took  short  flights,  awkwardly  of  course, 
but  safely.  One  of  them  was  raised  about  40  feet  vertically 
and  came  down  again  so  gently  that  he  felt  no  jar  upon  alight- 
ing. Others  glided  from  70  to  150  feet,  and  all  agreed  that 
the  sensation  of  coasting  on  the  air  was  delightful,  although 
they  were  somewhat  timid  about  tempting  fate  too  many  times. 
Any  young,  active  man  can  become  expert  in  a week  with  either 
of  these  machines. 

We  performed  nothing  like  continuous  soaring  with  any  of 
the  machines.  The  fluctuations  of  the  wind  were  entirely  too 
irregular  to  be  availed  of ; for  a wind  gust,  which  tossed  a 
machine  up,  was  almost  immediately  succeeded  by  a lull  which 
let  it  down  again.  If  we  had  had  a long,  straight  ridge,  bare  of 
trees  at  its  summit,  and  a suitable  wind  blowing  at  right  angles 
thereto,  we  would  have  attempted  to  have  sailed  horizontally 
along  the  top  of  the  ridge,  transversely  to  the  resulting  ascend- 
ing current.  This  manoeuvre  is  frequently  and  easily  performed 
by  the  soaring  birds  over  the  edge  of  a belt  of  trees.  They 


RECENT  EXPERIMENTS  IN  GLIDING  FLIGHT. 


69 


ride  across  the  face  of  the  ascending  aerial  billow,  decompos- 
ing its  upward  trend  into  propulsion  as  well  as  support.  The 
feat  should  be  performable  by  man,  and  should,  in  my  judg- 
ment, be  attempted  before  circling  flight  is  tried.  It  requires, 
of  course,  that  the  equilibrium  shall  be  first  mastered,  and  also 
that  the  angle  of  flight  shall  be  flatter  than  with  our  machines. 
This  was,  as  has  been  seen,  from  8 degrees  to  1 1 degrees,  or  a 
descent  of  i in  7 or  i in  5.  Now,  the  soaring  birds  generally 
sail  at  angles  of  4 degrees  to  6 degrees,  or  a descent  of  i in 
15  to  l in  9,  and  hence  they  lose  very  much  less  elevation. 
This  disadvantage  in  the  machines  resulted  from  the  increased 
head  resistance  due  to  the  framing  and  spars  as  compared 
with  the  wing  edges  of  the  birds,  and  especially  from  the  fact 
that  in  order  to  give  the  man  easy  command  over  his  move- 
ments and  to  let  him  land  on  his  feet,  he  has  to  be  in  the  natural 
erect  position.  This  produces  a body  resistance  due  to  about 
5 square  feet  of  surface,  while  it  would  be  that  due  to  only  about 
I square  foot  if  the  man  were  placed  horizontally,  as  is  the  body 
of  the  bird.  It  is  probable,  however,  that  the  machines  can  be 
improved  in  this  respect,  and  that  flatter  angles  of  flight  will  be 
obtained  than  those  recorded  herein. 

The  apparatus  of  Mr.  Butusov,  like  that  of  Le  Bris,  had  been 
inspired  by  watching  the  sailing  of  the  albatross  in  southern 
latitudes.  He  stated  that  having  begun  by  experimenting  with 
the  main  wings,  he  had  been  led  to  add  various  adjuncts,  such 
as  the  keels  and  the  top  aeroplane  in  order  to  improve  the  sta- 
bility. It  was  no  part  of  the  original  programme  to  test  such  a 
machine,  but  in  view  of  the  degree  of  success  said  to  have  been 
attained  both  by  Le  Bris  and  by  Mr.  Butusov,  it  was  determined 
to  give  the  apparatus  a trial. 

As  it  weighed  190  pounds,  and  the  operator’s  own  weight 
was  130  pounds,  a total  of  320  pounds,  it  was  necessary  to 
furnish  special  appliances  for  launching  the  machine.  This  was 
provided  for  by  building  an  inclined  trestle  work,  which  con- 
sisted in  a pair  of  tallowed  guides  or  ways,  8 feet  apart,  de- 
scending at  an  angle  of  23  degrees  down  the  slope  of  the  sand 
hill  selected,  the  top  being  94  feet  and  the  bottom  67  feet  above 


70 


THE  AERONAUTICAL  ANNUAL. 


the  lake.  The  last  lO  feet  of  these  launching  ways  was  hori- 
zontal, and  connected  with  the  sloping  portion  by  a curve  of 
5 feet  radius.  The  ways  stood  about  1 1 feet  above  the  side 
of  the  hill,  the  central  space  between  them  being  entirely  unob- 
structed, the  supports  being  braced  by  raking  posts  and  braces. 
The  trestle  faced  due  north,  so  as  to  avail  of  the  north  wind, 
which,  blowing  down  the  whole  length  of  Lake  Michigan, 
arrived  with  fewer  of  the  whirls  and  eddies  than  prev'ailed  with 
the  winds  coming  from  the  south,  south-east,  or  south-west. 
These  had  been  disturbed  by  blowing  over  the  sand  hills,  and 
it  is  a peculiarity  well  worthy  of  note  by  other  experimenters 
that  they  will  find  it  much  preferable  to  avail  of  winds  which 
have  traversed  across  a sheet  of  water  or  a level  plain  than  of 
those  which  have  come  over  hills,  trees,  or  other  obstacles. 

This  fixed  position  of  the  launching  ways,  however,  unfortu- 
nately required  the  waiting  for  a north  wind  to  blow  before 
experiments  could  be  conducted  with  this  apparatus.  The  pre- 
vailing winds  in  September  were  from  the  south,  and  there  were 
many  storms,  so  that  the  instances  were  rare  indeed,  during  the 
three  weeks  which  elapsed  after  the  trestle  and  apparatus  were 
completed,  when  the  wind  came  from  the  right  direction,  and 
with  just  the  velocity  (i8  to  25  miles  per  hour)  which  was  de- 
sired. Hence  the  machine  was  not  given  that  complete  and 
thorough  test  which  it  would  have  received  had  the  inventor 
accepted  my  proposal  to  launch  from  ways  rigged  up  on  a 
floating  barge,  which  might  have  been  anchored  or  towed 
against  any  wind  of  suitable  velocity. 

Before  proceeding  with  the  tests,  the  whole  apparatus  was 
carefully  measured.  It  was  ascertained  that  the  whole  sec- 
tional area  of  the  framing,  spars,  wing  edges,  ribs,  stanchions, 
guys,  cords,  etc.,  including  5 square  feet  for  the  body  of  the 
operator,  was  44.92  square  feet,  reduced,  however,  by  reason  of 
the  rounding  of  the  parts  to  an  equivalent  of  33.28  square  feet, 
which  area,  multiplied  by  the  pressure,  would  give  the  head 
resistance ; that  the  apparatus  would  require  a relative  speed 
of  25  miles  an  hour  (3.06  pounds  per  square  foot  pressure)  in 
order  to  float  it  at  an  angle  of  incidence  of  -\-2  degrees,  and 


RECENT  EXPERIMENTS  IN  GLIDING  FLIGHT. 


71 


that,  therefore,  if  Lilienthal’s  coefficients  were  used,  the  total 
resistances  would  be : 

Head  resistance,  33.28  sq.  ft.  X 3.06  lbs.  = 101.83  lt)S. 

Tangential  component,  266  sq.  ft.  X 3.06  lbs.  X 0.008  = 6.5  i “ 
Retarding  component,  320  lbs.  X (sin  2°  = 0.035)  — H-20  “ 

Total,  1 19-54  “ 

So  that  the  angle  of  descent  might  be  expected  to  be : 

320  lbs.  _ ^ 2 g 22  degrees. 

120  lbs.  ' ^ 

These  calculations  were  closely  verified,  as  in  the  case  of  the 
other  two  machines. 

It  was  the  15  th  of  September  (1896)  before  a proper  wind 
served.  It  then  set  in  from  the  north  about  noon  and  blew 
28  miles  an  hour.  The  apparatus  was  accordingly  placed  in 
the  ways,  tested  as  to  fit  by  running  it  up  and  down  restrained 
by  head  and  tail  ropes,  and  then  it  was  placed  upon  the  level 
portion  of  the  ways  facing  the  wind.  Additional  guy  lines  were 
fastened  to  the  wings,  and  Mr.  Butusov  got  into  the  machine. 
The  guy  lines  were  manned,  and  the  apparatus  was  suffered  to 
rise  2^  to  3 feet  above  the  ways,  in  order  to  test  its  balancing 
and  the  degree  of  control  of  the  operator  over  its  movements. 

This  appeared  to  be  complete.  A very  slight  step  to  the 
front  or  rear  sufficed  to  depress  or  to  raise  the  head  of  the 
machine,  and  the  side  motions  were  equally  sensitive.  The  sup- 
port was  found  to  be  ample  from  a 28-mile  wind,  and  it  was 
apparent  that  the  great  range  of  motion  provided  for  the  oper- 
ator would  give  him  command  of  the  machine  at  all  angles  of 
incidence.  The  apparatus  was  then  hauled  down  by  the  guy 
lines  and  settled  back  upon  the  ways  squarely,  resting  thereon 
by  means  of  four  sliding  shoes  projecting  from  the  machine  on 
a line  with  the  top  of  the  boat-like  body.  It  is  shown  in  that 
position  by  Fig.  i,  Plate  IX. 

It  was  desired  next  to  launch  it  in  ballast,  and  also  to  test  it 
as  a kite,  and  preparations  were  begun,  for  that  purpose ; but  a 


72 


THE  AERONAUTICAL  ANNUAL. 


small  rip  having  been  discovered  in  one  of  the  wing  coverings, 
and  a buckling  in  one  of  the  braces,  it  was  thought  more  pru- 
dent to  repair  these  before  proceeding  further,  and  the  machine 
was  removed  from  the  ways. 

The  wind  changed  to  the  south-west  in  the  night,  but  on  the 
17th  it  again  blew  from  the  north,  with  a speed,  however,  of  but 
12  miles  per  hour.  In  the  hope  of  its  freshening,  the  machine 
was  got  into  the  ways,  loaded  with  130  pounds  of  sand  in  bags, 
and  rigged  as  a kite,  by  fastening  a bridle  to  the  keel  of  the 
boat  and  leading  therefrom  a long  rope  passing  through  a pulley 
fastened  to  a post  in  the  sand,  250  feet  away  on  the  beach. 
This  rope  was  handled  by  four  men,  with  instructions  to  run 
with  it  so  as  to  take  up  the  slack  as  soon  as  the  apparatus  left 
the  ways.  Four  guy  lines,  hanging  down  from  the  front  and 
rear,  and  from  each  wing  of  the  machine,  were  likewise 
manned,  in  order  to  control  the  movements  of  the  kite  in  case 
of  need. 

All  being  ready,  the  restraining  line  was  cut  and  the  machine 
slid  down  the  tallowed  ways  and  took  the  air  fair  and  level.  It 
went  horizontally  some  20  feet,  but  its  motion  was  then  checked 
by  the  friction  on  the  sand  of  the  kite  line,  which  the  crew,  gaz- 
ing open-mouthed  at  the  sight,  failed  to  haul  in  as  the  machine 
flew  forward.  This  check  was  sufficient  to  overcome  the  initial 
velocity  proper  to  the  machine,  and  the  wind  (12  miles  an  hour) 
was  insufficient  to  sustain  it.  The  apparatus  glided  downward 
and  landed  squarely  on  its  keel  about  100  feet  from  the  end  of 
the  ways,  a descent  of  about  i in  2.  The  tip  of  one  wing  struck 
the  hillside,  but  no  harm  was  done  as  it  flexed.  Some  three  or  four 
of  the  stanchions  of  the  boat  frame  were,  however,  broken.  These 
were  replaced  in  two  hours,  but  the  wind  had  fallen  so  light  by 
that  time  that  the  experiment  could  not  be  repeated. 

To  test  the  apparatus  properly  a north  wind  of  about  25  miles 
per  hour  was  required.  This  did  not  set  in  again  till  just  before 
the  advancing  season  compelled  the  breaking  up  of  camp  and 
returning  to  the  city.  On  the  19th  of  September  the  equinoc- 
tial storm  set  in  and  blew  from  the  north-west  56  to  60  miles  an 
hour.  Another  gale  of  60  miles  an  hour  blew  on  the  22d,  ac- 


RECENT  EXPERIMENTS  IN  GLIDING  FLIGHT. 


73 


companied  by  heavy  rains.  These  were  followed  by  southerly 
winds,  so  that  it  was  the  26th  before  the  machine  could  be  tested 
again.  A wind  then  set  in  from  the  north-east,  with  a speed  of 
18  miles  an  hour,  and  although  this  was  quartering,  instead  of 
dead  ahead  as  was  desired,  it  was  determined  to  launch  the 
apparatus.  This  was  first  attempted  with  the  operator  in  the 
machine,  but  as  the  quartering  wind  greatly  increased  the  friction 
of  the  launching  ways  and  diminished  the  required  initial  speed, 
the  operator  was  replaced  by  90  pounds  of  sand  in  bags,  and  a 
rope  was  fastened  to  the  front  of  the  machine  in  order  to  increase 
its  velocity  by  pulling  thereon.  The  apparatus  went  off,  but  as 
soon  as  it  had  fairly  left  the  end  of  the  ways,  the  quartering 
wind  swerved  the  head  of  the  machine  around,  and  it  took  a 
descending  north-westerly  course,  describing  a curved  path. 
The  tip  of  the  left  wing  then  struck  the  top  of  a tree,  swing- 
ing the  machine  around  further,  and  then  this  same  wing 
struck  the  hillside  and  was  broken.  The  machine  then  fell  to 
the  ground,  landing  upon  its  keel  about  75  feet  from  the  end  of 
the  ways,  and  a number  of  ribs  and  stanchions  were  broken,  so 
that  the  repairs,  if  made,  would  probably  have  occupied  a day 
or  two. 

It  was  evident  that  the  machine  was  moderately  stable ; that 
on  neither  this  nor  on  the  previous  trial  would  the  operator 
have  been  hurt  if  he  had  been  in  the  machine ; but  it  was  also 
evident  that  the  apparatus,  as  then  proportioned,  glided  at  too 
steep  an  angle  to  perform  soaring  flight ; that  it  would  lose  so 
much  altitude  when  going  with  the  wind  that  the  loss  would 
not  be  recuperated  when  turned  to  face  the  wind.  It  was  rec- 
ognized that  this,  as  well  as  the  other  two  machines,  could  be 
modified  so  as  to  materially  reduce  the  head  resistance  and 
thereby  flatten  the  angle  of  descent,  but  the  season  was  so  far 
advanced,  the  weather  so  inclement,  that  it  was  decided  to  break 
up  camp  and  to  return  to  the  city.  This  was  done  on  the  27th 
of  September. 

Such  were  the  experiments.  They  occupied  an  aggregate 
of  seven  or  eight  weeks  in  the  field,  they  were  carried  on  with- 
out the  slightest  accident  to  the  operators,  and  they  made  mani- 


74 


THE  AERONAUTICAL  ANNUAL. 


fest  several  important  conclusions.  The  first  is  that  it  is  reason- 
ably  safe  to  experiment  with  full-sized  machines,  if  the  methods 
and  writings  of  Lilienthal  be  previously  studied.  The  second  is 
that  experiments  with  full-sized  machines,  carrying  a man,  are 
likely  to  be  more  instructive  and  fruitful  of  eventual  progress 
than  experiments  with  models.  The  third  is  the  inference  that 
it  is  probably  possible  to  evolve  an  apparatus  with  automatic 
stability  in  the  wind,  but  that  in  order  to  do  so,  there  must  be 
some  moving  parts,  apart  from  the  man,  in  order  to  restore  the 
balance  as  often  as  it  is  compromised.  The  fourth  conclusion 
is  that  the  problem  of  automatic  stability  will  be  most  easily 
worked  out  with  a light  apparatus,  so  light  as  to  enable  the 
operator  to  carry  it  with  ease,  and  so  arranged  as  to  enable  him 
to  use  his  legs  in  landing.  The  fifth  conclusion  is  that  it  will 
require  a good  deal  of  experimenting  to  adjust  the  working 
parts,  to  regulate  the  springs,  and  to  discover  hidden  defects, 
before  it  will  be  quite  safe  to  try  to  perform  soaring  feats  in  the 
wind.  The  sixth  is  that  the  incessant  fluctuations  of  the  wind, 
which  so  very  greatly  complicate  the  problem  of  maintaining 
automatic  stability,  probably  result  from  the  rotary  action  of  its 
billows,  and  future  experimenters  are  urgently  advised  to  study 
this  action  and  to  endeavor  to  meet  it. 

A word  or  two  of  caution  may  also  be  given.  It  is  best  to 
begin  experimenting  with  a new  machine  in  short  and  low  glid- 
ing flights  over  bare  and  soft  sand  hills,  but  more  ambitious 
flights  and  soaring  feats  should  be  attempted  first  over  a sheet 
of  water  to  mitigate  the  fall  should  anything  go  wrong.  Ex- 
periments should  not  be  tried  in  high  or  gusty  winds,  and  the 
apparatus  should  be  frequently  examined  and  kept  in  con- 
stantly perfect  order.  Wire  stays  should  be  employed  as  spar- 
ingly as  possible.  Not  only  do  they  vibrate  when  the  machine 
is  under  way,  and  so  increase  the  resistance,  but  they  get  loose 
and  allow  the  apparatus  to  become  distorted.  It  is  well  to  fly  a 
model  of  a projected  apparatus  as  a kite,  but  it  does  not  follow 
that  a satisfactory  kite  will  make  a good  flying-machine,  because 
the  required  angles  of  incidence  are  so  different.  A good  kite  will 
fly  steadily  at  an  angle  of  20  or  30  degrees  with  the  wind,  but 


6I^V€R  'C.  BERGDOiii* 


Plate  XIV. 


CAMP  CHANUTE,  1896,  SOUTHERN  SHORE  OF  LAKE  MICHIGAN. 


BLUE  HILL  METEOROLOGICAL  .OBSERVATORY. 
From  the  Northwest,  showing  New  Construction.  See  p.  208. 


RECENT  EXPERIMENTS  IN  GLIDING  FLIGHT. 


75 


a good  flying-machine  needs  to  fly  at  an  angle  of  2 to  5 degrees 
to  reduce  the  drift  to  the  lowest  possible. 

I do  not  know  how  much  further  I shall  carry  on  these  experi- 
ments. They  were  made  wholly  at  my  own  expense,  in  the 
hope  of  gaining  scientific  knowledge  and  without  the  expecta- 
tion of  pecuniary  profit.  I believe  the  latter  to  be  still  afar  off, 
for  it  seems  unlikely  that  a commercial  machine  will  be  per- 
fected very  soon.  It  will,  in  my  judgment,  be  worked  out  by  a 
process  of  evolution : one  experimenter  finding  his  way  a cer- 
tain distance  into  the  labyrinth,  the  next  penetrating  further, 
and  so  on,  until  the  very  centre  is  reached  and  success  is  won. 
In  the  hope,  therefore,  of  making  the  way  easier  to  others,  I 
have  set  down  the  relation  of  these  experiments,  perhaps  at 
tedious  length,  so  that  other  searchers  may  carry  the  work  of 
exploration  further. 


SOARING  FLIGHT. 


By  Octave  Chanute. 

(^Reprinted  from  American  Aeronautics,*  April,  igog.~) 

Note.  — This  paper,  written  for  the  International  Aeronautical  Congress  of  1907  and 
revised  in  1909,  is  here  substituted  for  the  articles  by  the  same  author  which  appeared 
in  The  Aeronautical  Annuals  of  1896  and  1897  referred  to  in  the  text. 

There  is  a wonderful  performance  daily  exhibited  in  southern 
climes  and  occasionally  seen  in  northerly  latitudes  in  summer, 
which  has  never  been  thoroughly  explained.  It  is  the  soaring 
or  sailing  flight  of  certain  varieties  of  large  birds  which  trans- 
port themselves  on  rigid  unflapping  wings  in  any  desired 
direction ; which,  in  winds  of  6 to  20  miles  per  hour,  circle,  rise, 
advance,  return  and  remain  aloft  for  hours  without  a beat  of 
wing,  save  for  getting  under  way  or  convenience  in  various 
maneuvers.  They  appear  to  obtain  from  the  wind  alone  all  the 
necessary  energy,  even  to  advancing  dead  against  that  wind. 
This  feat  is  so  much  opposed  to  our  general  ideas  of  physics 
that  those  who  have  not  seen  it  sometimes  deny  its  actuality, 
and  those  who  have  only  occasionally  witnessed  it  subsequently 
doubt  the  evidence  of  their  own  eyes.  Others,  who  have  seen 
the  exceptional  performances,  speculate  on  various  explana- 
tions, but  the  majority  give  it  up  as  a sort  of  “ negative 
gravity.” 

The  writer  of  this  paper  published  in  the  “ Aeronautical 
Annual”^  for  1896  and  1897  an  article  upon  the  sailing  flight 
of  birds,  in  which  he  gave  a list  of  the  authors  who  had  described 
such  flight  or  had  advanced  theories  for  its  explanation,  and  he 
passed  these  in  review.  He  also  described  his  own  observa- 
tions and  submitted  some  computations  to  account  for  the 
observed  facts.  These  computations  were  correct  as  far  as 
they  went,  but  they  were  scanty.  It  was,  for  instance,  shown 
convincingly  by  analysis  that  a gull  weighing  2.188  pounds, 
with  a total  supporting  surface  of  2.015  square  feet,  a maximum 
body  cross-section  of  0.126  square  feet  and  a maximum  cross- 
section  of  wing  edges  of  0.098  square  feet,  patrolling  on  rigid 
wings  (soaring)  on  the  weather  side  of  a steamer  and  maintain- 

' Aeronautics,  published  monthly  at  1777  Broadway,  New  York.  Seventh  volume 
begins  with  issue  of  July,  1910.  ^3.00  per  annum,  U.S.,  Ss-so  foreign.  Specimen  copies 
25  cents. 

2 The  “Aeronautical  Annuals”  of  1895,  1896,  and  1897  may  be  found  in  the  public 
libraries  of  every  city  in  the  United  States  having  a population  of  100,000  or  more.  — Ed. 

(76) 


SOARING  FLIGHT. 


77 


ing  an  upward  angle  or  attitude  of  5 degrees  to  7 degrees  above 
the  horizon,  in  a wind  blowing  12.78  miles  an  hour,  which  was 
deflected  upward  10  degrees  to  20  degrees  by  the  side  of  the 
steamer  (these  all  being  carefully  observed  facts),  was  perfectly 
sustained  at  its  own  “relative  speed”  of  17.88  miles  per  hour 
and  extracted  from  the  upward  trend  of  the  wind  sufficient 
energy  to  overcome  all  the  resistances,  this  energy  amounting 
to  6.44  foot-pounds  per  second.  It  was  shown  that  the  same 
bird  in  flapping  flight  in  calm  air,  with  an  attitude  or  incidence 
of  3 degrees  to  5 degrees  above  the  horizon  and  a speed  of  20.4 
miles  an  hour  was  well  sustained  and  expended  5.88  foot- 
pounds per  second,  this  being  at  the  rate  of  204  pounds  sus- 
tained per  horse  power.  It  was  stated  also  that  a gull  in  its 
observed  maneuvers,  rising  up  from  a pile  head  on  unflapping 
wings,  then  plunging  forward  against  the  wind  and  subsequently 
rising  higher  than  his  starting  point,  must  either  time  his 
ascents  and  descents  exactly  with  the  variations  in  wind  veloci- 
ties, or  must  meet  a wind  billow  rotating  on  a horizontal  axis 
and  come  to  a poise  on  its  crest,  thus  availing  of  an  ascending 
trend. 

But  the  observations  failed  to  demonstrate  that  the  variations 
of  the  wind  gusts  and  the  movements  of  the  bird  were  abso- 
lutely synchronous,  and  it  was  conjectured  that  the  peculiar 
shape  of  the  soaring  wing  of  certain  birds,  as  differentiated  from 
the  flapping  wing,  might,  when  experimented  upon,  hereafter 
account  for  the  performance. 

These  computations,  however  satisfactory  they  were  for  the 
speed  of  winds  observed,  failed  to  account  for  the  observed 
spiral  soaring  of  buzzards  in  very  light  winds  and  the  writer  was 
compelled  to  confess:  “Now,  this  spiral  soaring  in  steady 
breezes  of  5 to  10  miles  per  hour  which  are  apparently  horizon- 
tal, and  through  which  the  bird  maintains  an  average  speed  of 
about  20  miles  an  hour,  is  the  mystery  to  be  explained.  It  is 
not  accounted  for,  quantitatively,  by  any  of  the  theories  which 
have  been  advanced,  and  it  is  the  one  performance  which  has 
led  some  observers  to  claim  that  it  was  done  through  ‘ aspira- 
tion,’ i.e.,  that  a bird  acted  upon  by  a current  actually  drew 
forward  into  that  current  against  its  exact  direction  of  motion.” 

A still  greater  mystery  was  propounded  by  the  few  observers 
who  asserted  that  they  had  seen  buzzards  soaring  in  a dead 
calm,  maintaining  their  elevation  and  their  speed.  Among 
these  observers  was  Mr.  E.  C.  Huffaker,  at  one  time  assistant 
experimenter  for  Professor  Langley.  The  writer  believed  and 


78 


THE  AERONAUTICAL  ANNUAL. 


said  then  that  he  must  in  some  way  have  been  mistaken,  yet,  to 
satisfy  himself,  he  paid  several  visits  to  Mr.  Hufifaker  in  Eastern 
Tennessee  and  took  along  his  anemometer.  He  saw  quite  a 
number  of  buzzards  sailing  at  a height  of  75  to  100  feet  in 
breezes  measuring  5 or  6 miles  an  hour  at  the  surface  of  the 
ground,  and  once  he  saw  one  buzzard  soaring  apparently  in  a 
dead  calm. 

The  writer  was  fairly  baffled.  The  bird  was  not  simply 
gliding,  utilizing  gravity  or  acquired  momentum,  he  was  actually 
circling  horizontally  in  defiance  of  physics  and  mathematics. 
It  took  two  years  and  a whole  series  of  further  observations  to 
bring  those  two  sciences  into  accord  with  the  facts. 

Curiously  enough  the  key  to  the  performance  of  circling  in  a 
light  wind  or  a dead  calm  was  not  found  through  the  usual  way 
of  gathering  human  knowledge,  i.e.,  through  observations  and 
experiment.  These  had  failed  because  I did  not  know  what  to 
look  for.  The  mystery  was,  in  fact,  solved  by  an  eclectic 
process  of  conjecture  and  computation,  but  once  these  compu- 
tations indicated  what  observations  should  be  made,  the  results 
gave  at  once  the  reasons  for  the  circling  of  the  birds,  for  their 
then  observed  attitude  and  for  the  necessity  of  an  independent 
initial  sustaining  speed  before  soaring  began.  Both  Mr.  Hufifa- 
ker and  myself  verified  the  data  many  times  and  I made  the 
computations. 

These  observations  disclosed  several  facts : 

1st.  That  winds  blowing  5 to  17  miles  per  hour  frequently 
had  rising  trends  of  10  degrees  to  15  degrees,  and  that  upon 
occasions  when  there  seemed  to  be  absolutely  no  wind,  there 
was  often  nevertheless  a local  rising  of  the  air  estimated  at  a 
rate  of  4 to  8 miles  or  more  per  hour.  This  was  ascertained  by 
watching  thistledown  and  rising  fogs  alongside  of  trees  or  hills 
of  known  height.  Every  one  will  readily  realize  that  when 
walking  at  the  rate  of  4 to  8 miles  an  hour  in  a dead  calm  the 
“ relative  wind  ” is  quite  inappreciable  to  the  senses  and  that 
such  a rising  air  would  not  be  noticed. 

2d.  That  the  buzzard,  sailing  in  an  apparently  dead  hori- 
zontal calm,  progressed  at  speeds  of  15  to  18  miles  per  hour, 
as  measured  by  his  shadow  on  the  ground.  It  was  thought 
that  the  air  was  then  possibly  rising  8.8  feet  per  second,  or  6 
miles  per  hour. 

3d.  That  when  soaring  in  very  light  winds  the  angle  of  inci- 
dence of  the  buzzards  was  negative  to  the  horizon  — i.e.,  that 
when  seen  coming  toward  the  eye,  the  afternoon  light  shone  on 


SOARING  FLIGHT. 


79 


the  back  instead  of  on  the  breast,  as  would  have  been  the  case 
had  the  angle  been  inclined  above  the  horizon. 

4th.  That  the  sailing  performance  only  occurred  after  the 
bird  had  acquired  an  initial  velocity  of  at  least  15  or  18  miles 
per  hour,  either  by  industrious  flapping  or  by  descending  from 
a perch. 

5th.  That  the  whole  resistance  of  a stuffed  buzzard,  at  a 
negative  angle  of  3 degrees  in  a current  of  air  of  15.52  miles 
per  hour,  was  0.27  pounds.  This  test  was  kindly  made  for  the 
writer  by  Prof.  A.  F.  Zahm  in  the  “wind  tunnel”  of  the 
Catholic  University  at  Washington,  D.C.,  who,  moreover,  stated 
that  the  resistance  of  a live  bird  might  be  less,  as  the  dried 
plumage  could  not  be  made  to  lie  smooth. 

This  particular  buzzard  weighed  in  life  4.25  pounds,  the  area 
of  his  wings  and  body  was  4.57  square  feet,  the  maximum 
cross-section  of  his  body  was  o.iio  square  feet,  and  that  of  his 
wing  edges  when  fully  extended  was  0.244  square  feet. 

With  these  data,  it  became  surprisingly  easy  to  compute  the 
performance  with  the  coefficients  of  Lilienthal  for  various  angles 
of  incidence  and  to  demonstrate  how  this  buzzard  could  soar 
horizontally  in  a dead  horizontal  calm,  provided  that  it  was  not 
a vertical  calm  and  that  the  air  was  rising  at  the  rate  of  4 or  6 
miles  per  hour,  the  lowest  observed,  and  quite  inappreciable 
without  actual  measuring. 

The  most  difficult  case  is  purposely  selected.  For  if  we 
assume  that  the  bird  has  previously  acquired  an  initial  mini- 
mum speed  of  17  miles  an  hour  (24.93  feet  per  second,  nearly 
the  lowest  measured),  and  that  the  air  was  rising  vertically  6 
miles  an  hour  (8.80  feet  per  second),  then  we  have  as  the  trend 
of  the  “ relative  wind  ” encountered : 

6 

— =0.353,  or  the  tangent  of  ig°  26' 

17 

which  brings  the  case  into  the  category  of  rising  wind  effects. 
But  the  bird  was  observed  to  have  a negative  angle  to  the  hori- 
zon of  about  3°,  as  near  as  could  be  guessed,  so  that  his  angle 
of  incidence  to  the  “relative  wind”  was  reduced  to  16”  26'. 

The  relative  speed  of  his  soaring  was  therefore : 

Velocity  = \/ 1 7^  -f-  6^  =•  18.03  miles  per  hour. 

At  this  speed,  using  the  Langley  coefficient  recently  practi- 
cally confirmed  by  the  accurate  experiments  of  Mr.  Eiffel,  the 
air  pressure  would  be  : 

18.03^  X 0.00327  = 1.063  pounds  per  square  foot. 


8o 


THE  AERONAUTICAL  ANNUAL. 


If  we  apply  Lilienthal’s  coefficients  for  an  angle  of  i6°  26', 
we  have  for  the  force  in  action : 

Normal:  4.57  X 1.063  0.912  = 4.42  pounds. 

Tangential:  4.57  X 1.063  X 0.074  = — 0.359  pounds. 
Which  latter,  being  negative,  is  a propelling  force. 

Thus  we  have  a bird  weighing  4.25  pounds  not  only 
thoroughly  supported,  but  impelled  forward  by  a force  of  0.359 
pounds,  at  17  miles  per  hour,  while  the  experiments  of  Prof. 
A.  F.  Zahm  showed  that  the  resistance  at  15.52  miles  per  hour 

172 

was  only  0.27  pounds,  or  0.27  X =0.324  pounds,  at  17 

15-52' 

miles  an  hour. 

These  are  astonishing  results  from  the  data  obtained,  and 
they  lead  to  the  inquiry  whether  the  energy  of  the  rising  air  is 
sufficient  to  make  up  the  losses  which  occur  by  reason  of  the 
resistance  and  friction  of  the  bird’s  body  and  wings,  which, 
being  rounded,  do  not  encounter  air  pressures  in  proportion  to 
their  maximum  cross-section. 

We  have  no  accurate  data  upon  the  coefficients  to  apply,  and 
estimates  made  by  myself  proved  to  be  much  smaller  than  the 
0.27  pounds  resistance  measured  by  Professor  Zanm,  so  that 
we  will  figure  with  the  latter  as  modified.  As  the  speed  is 
17  miles  per  hour,  or  24.93  per  second,  we  have  for  the 
work : 

Work  done,  0.324  X 24.93  = 8.07  foot-pounds  per  second. 

Corresponding  energy  of  rising  air  is  not  sufficient  at  4 miles 
per  hour.  This  amounts  to  but  2.10  foot-pounds  per  second, 
but  if  we  assume  that  the  air  was  rising  at  the  rate  of  7 miles 
per  hour  ( 1 0.26  feet  per  second ) , at  which  the  pressure  with  the 
Langley  coefficient  would  be  0.16  pounds  per  square  foot,  we 
have  on  4.57  square  feet  for  energy  of  rising  air:  4.57  X O.16 
X 10.26  = 7.50  foot-pounds  per  second,  which  is  seen  to  be  still 
a little  too  small,  but  well  within  the  limits  of  error,  in  view  of 
the  hollow  shape  of  the  bird’s  wings,  which  receive  greater 
pressure  than  the  flat  planes  experimented  upon  by  Langley. 

These  computations  were  chiefly  made  in  January,  1899,  and 
were  communicated  to  a few  friends,  who  found  no  fallacy  in 
them,  but  thought  that  few  aviators  would  understand  them  if 
published.  They  were  then  submitted  to  Prof.  C.  F.  Mar- 
vin of  the  Weather  Bureau,  who  is  well  known  as  a skilful 
physicist  and  mathematician.  He  wrote  that  they  were,  theo- 
retically, entirely  sound  and  quantitatively,  probably,  as  accurate 


SOARING  FLIGHT. 


8l 


as  the  present  state  of  the  measurements  of  wind  pressures 
permitted.  The  writer  determined,  however,  to  withhold  pub- 
lications until  the  feat  of  soaring  flight  had  been  performed  by 
man,  partly  because  he  believed  that,  to  ensure  safety,  it  would 
be  necessary  that  the  machine  should  be  equipped  with  a motor 
in  order  to  supplement  any  deficiency  in  wind  force. 

The  feat  would  have  been  attempted  in  1902  by  Wright 
Brothers  if  the  local  circumstances  had  been  more  favorable. 
They  were  experimenting  on  “Kill  Devil  Hill,”  near  Kitty 
Hawk,  N.C.  This  sand  hill,  about  100  feet  high,  is  bordered 
by  a smooth  beach  on  the  side  whence  comes  the  sea  breezes 
but  has  marshy  ground  at  the  back.  Wright  Brothers  were 
apprehensive  that  if  they  rose  on  the  ascending  current  of  air 
at  the  front  and  began  to  circle  like  the  birds,  they  might  be 
carried  by  the  descending  current  past  the  back  of  the  hill  and 
land  in  the  marsh.  Their  gliding  machine  offered  no  greater 
head  resistance  in  proportion  than  the  buzzard,  and  their  glid- 
ing angles  of  descent  are  practically  as  favorable,  but  the  birds 
performed  higher  up  in  the  air  than  they. 

Professor  Langley  said  in  concluding  his  paper  upon  “ The 
Internal  Work  of  the  Wind  ” : 

“ The  final  application  of  these  principles  to  the  art  of  aero- 
dromics  seems,  then,  to  be,  that  while  it  is  not  likely  that  the 
perfected  aerodrome  will  ever  be  able  to  dispense  altogether 
with  the  ability  to  rely  at  intervals  on  some  internal  source  of 
power,  it  will  not  be  indispensable  that  this  aerodrome  of  the 
future  shall,  in  order  to  go  any  distance — even  to  circumnavi- 
gate the  globe  without  alighting  — need  to  carry  a weight  of 
fuel  which  would  enable  it  to  perform  this  journey  under  con- 
ditions analogous  to  those  of  a steamship,  but  that  the  fuel  and 
weight  need  only  be  such  as  to  enable  it  to  take  care  of  itself  in 
exceptional  moments  of  calm.” 

Now  that  dynamic  flying  machines  have  been  evolved  and 
are  being  brought  under  control,  it  seems  to  be  worth  while  to 
make  these  computations  and  the  succeeding  explanations 
known,  so  that  some  bold  man  will  attempt  the  feat  of  soaring 
like  a bird.  The  theory  underlying  the  performance  in  a rising 
wind  is  not  new,  it  has  been  suggested  by  Penaud  and  others, 
but  it  has  attracted  little  attention,  because  the  exact  data  and 
the  maneuvers  required  were  not  known  and  the  feat  had  not 
yet  been  performed  by  a man.  The  puzzle  has  always  been 
to  account  for  the  observed  act  in  very  light  winds,  and  it  is 
hoped  that  by  the  present  selection  of  the  most  difficult  case 


82 


THE  AERONAUTICAL  ANNUAL. 


to  explain — i.e.,  the  soaring  in  a dead  horizontal  calm  — some- 
body will  attempt  the  exploit. 

The  following  are  deemed  to  be  the  requisites  and  maneu- 
vers to  master  the  secrets  of  soaring  flight : 

1st.  Develop  a dynamic  flying  machine  weighing  about  one 
pound  per  square  foot  of  area,  with  stable  equilibrium  and 
under  perfect  control,  capable  of  gliding  by  gravity  at  angles 
of  one  in  ten  ( 5^°)  in  still  air. 

2d.  Select  locations  where  soaring  birds  abound  and  occa- 
sions where  rising  trends  of  gentle  winds  are  frequent  and  to  be 
relied  on. 

3d.  Obtain  an  initial  velocity  of  at  least  25  feet  per  second 
before  attempting  to  soar. 

4th.  So  locate  the  center  of  gravity  that  the  apparatus  shall 
assume  a negative  angle,  fore  and  aft,  of  about  3°.  Calcula- 
tions show,  however,  that  sufficient  propelling  force  may  still 
exist  at  o®,  but  disappears  entirely  at  + 4°. 

•5th.  Circle  like  the  bird.  Simultaneously  with  the  steering, 
incline  the  apparatus  to  the  side  toward  which  it  is  desired  to 
turn,  so  that  the  centrifugal  force  shall  be  balanced  by  the  cen- 
tripetal force.  The  amount  of  the  required  inclination  depends 
upon  the  speed  and  on  the  radius  of  the  circle  swept  over. 

6th.  Rise  spirally  like  the  bird.  Steer  with  the  horizontal 
rudder,  so  as  to  descend  slightly  when  going  with  the  wind  and 
to  ascend  when  going  against  the  wind.  The  bird  circles  over 
one  spot  because  the  rising  trends  of  wind  are  generally  con- 
fined to  small  areas  or  local  chimneys,  as  pointed  out  by  Sir 
H.  Maxim  and  others. 

7th.  Once  altitude  is  gained,  progress  may  be  made  in  any 
direction  by  gliding  downward  by  gravity. 

The  bird’s  flying  apparatus  and  skill  are  as  yet  infinitely 
superior  to  those  of  man,  but  there  are  indications  that  within 
a few  years  the  latter  may  evolve  more  accurately  proportioned 
apparatus  and  obtain  absolute  control  over  it. 

It  is  hoped,  therefore,  that  if  there  be  found  no  radical  error 
in  the  above  computations,  they  will  carry  the  conviction  that 
soaring  flight  is  not  inaccessible  to  man,  as  it  promises  great 
economies  of  motive  power  in  favorable  localities  of  rising 
winds. 

The  writer  will  be  grateful  to  experts  who  may  point  out  any 
mistake  committed  in  data  or  calculations,  and  will  furnish 
additional  information  to  any  aviator  who  may  wish  to  attempt 
the  feat  of  soaring. 


[From  Aero.  Ann.,  1895.] 


DARWIN’S  OBSERVATIONS. 


Under  the  date  of  April  27,  1834,  in  his  journaU  kept  dur- 
ing the  voyage  of  the  “ Beagle  ” round  the  world,  Mr.  Darwin, 
after  considering  the  manner  in  which  vultures  ^ find  their  food, 
writes  as  follows : 

“ Often  when  lying  down  to  rest  on  the  open  plains,  on  look- 
ing upwards  I have  seen  carrion-hawks  sailing  through  the  air 
at  a great  height.  Where  the  country  is  level  I do  not  believe 
a space  of  the  heavens  of  more  than  fifteen  degrees  above  the 
horizon  is  commonly  viewed  with  any  attention  by  a person 
either  walking  or  on  horseback.  If  such  be  the  case,  and  the 
vulture  is  on  the  wing  at  a height  of  between  three  and  four 
thousand  feet,  before  it  could  come  within  the  range  of  vision, 
its  distance  in  a straight  line  from  the  beholder’s  eye  would  be 
rather  more  than  two  British  miles.  Might  it  not  thus  readily 
be  overlooked?  When  an  animal  is  killed  by  the  sportsman  in 
a lonely  valley,  may  he  not  all  the  while  be  watched  from  above 
by  the  sharp-sighted  bird?  And  will  not  the  manner  of  its 
descent  proclaim  throughout  the  district  to  the  whole  family  of 
carrion-feeders  that  their  prey  is  at  hand  ? 

“ When  the  condors  are  wheeling  in  a flock  round  and  round 
any  spot,  their  flight  is  beautiful.  Except  when  rising  from  the 
ground,  I do  not  recollect  ever  having  seen  one  of  these  birds 
flap  its  wings.  Near  Lima,  I watched  several  for  nearly  half  an 
hour  without  once  taking  off  my  eyes.  They  moved  in  large 
curves,  sweeping  in  circles,  descending  and  ascending  without 
giving  a single  flap.  As  they  glided  close  over  my  head,  I 

^ A Naturalist's  Voyage.  Journal  of  Researches  into  the  Natural  History  and  Geology 
of  the  countries  visited  during  the  voyage  of  H.M.S.  “Beagle”  round  the  World.  By 
Charles  Darwin,  M.A.,  F.R.S.  London.  1845. 

(83) 


84 


THE  AERONAUTICAL  ANNUAL. 


intently  watched  from  an  oblique  position  the  outlines  of  the 
separate  and  great  terminal  feathers  of  each  wing;  and  these 
separate  feathers,  if  there  had  been  the  least  vibratory  move- 
ment, would  have  appeared  as  if  blended  together ; but  they 
were  seen  distinct  against  the  blue  sky. 

“ The  head  and  neck  were  moved  frequently,  and  apparently 
with  force;  and  the  extended  wings  seemed  to  form  the  fulcrum 
on  which  the  movements  of  the  neck,  body,  and  tail  acted.  If 
the  bird  wished  to  descend,  the  wings  were  for  a moment  col- 
lapsed ; and  when  again  expanded  with  an  altered  inclination, 
the  momentum  gained  by  the  rapid  descent  seemed  to  urge  the 
bird  upwards  with  the  even  and  steady  movement  of  a paper 
kite.  In  the  case  of  any  bird  soaring,  its  motion  must  be 
sufficiently  rapid,  so  that  the  action  of  the  inclined  surface  of  its 
body  on  the  atmosphere  may  counterbalance  its  gravity.  The 
force  to  keep  up  the  momentum  of  a body  moving  in  a hori- 
zontal plane  in  the  air  (in  which  there  is  so  little  friction)  cannot 
be  great,  and  this  force  is  all  that  is  wanted. 

“ The  movement  of  the  neck  and  body  of  the  condor,  we  must 
suppose,  is  sufficient  for  this.  However  this  may  be,  it  is  truly 
wonderful  and  beautiful  to  see  so  great  a bird,  hour  after  hour, 
without  any  apparent  exertion,  wheeling  and  gliding  over 
mountain  and  river.” 


[From  Aero.  Ann.,  1896.] 


HOW  A BIRD  SOARS. 


By  Professor  William  H.  Pickering,  of  Harvard  Observatory. 


By  “soaring”  is  meant  the  upward  spiral  progress  of  a bird, 
without  apparent  muscular  effort.  This  action  may  be  observed 
in  this  part  of  the  world  to  particular  advantage,  in  the  case  of 
certain  large  hawks.  The  following  explanation  of  the  prin- 
ciple of  soaring  is  extracted  from  an  article  which  I published 
in  “Science,”  1889,  p.  245,  and  is,  I believe,  the  first  descrip- 
tion of  the  process  which  ascribes  to  gusts  of  wind  their  true 
influence  in  the  production  of  the  phenomenon: 

“ Whenever  there  is  a high  wind,  such  as  is  undoubtedly  re- 
quired by  a soaring  bird,  we  know  that  the  air  pressure  is  not 
uniform,  that  the  wind  comes  in  gusts.  Those  familiar  with 
mountain  summits  know  that  the  same  phenomena  are  observed 
in  the  upper  atmosphere  as  at  the  surface  of  the  ground.  If  we 
were  travelling  along  with  such  a wind  in  a balloon,  the  gusts 
would  not  be  so  severe,  but  they  would  be  of  longer  duration. 

A B 

“ Imagine,  now,  a bird  travelling  from  A to  B,  in  the  same 
direction  as  the  wind,  and  with  its  mean  velocity.  When  the 
wind  is  uniform,  it  seems  to  him  that  he  is  in  a dead  calm. 
When  a gust  comes,  the  wind  seems  to  blow  from  A.  It  carries 
him  along  faster ; and  when  it  ceases  the  wind  seems  to  blow 
from  B.  It  therefore  affects  him  precisely  as  if  he  were  in  an 
alternating  current  of  wind. 

“ Suppose,  now,  that  he  is  drifting  towards  B with  a velocity 
equal  to  that  of  the  wind,  and  travelling  at  right  angles  to  A B 
with  such  a velocity  that  he  can  move  along  horizontally  with- 
out falling  towards  the  earth.  Suddenly  a gust  overtakes  him 

(85) 


86 


THE  AERONAUTICAL  ANNUAL. 


from  the  direction  of  A.  He  at  once  turns  towards  it,  and  his 
velocity  relative  to  it  is  sufficient  to  raise  him  in  the  air.  It 
tends  to  carry  him  more  rapidly  towards  B ; and  when  his 
velocity  relative  to  it  has  sunk  to  the  same  value  as  before,  and 
he  again  travels  horizontally,  he  turns  again  at  right  angles  to 
the  line  AB,  but  in  the  opposite  direction  to  that  which  he  had 
before.  Presently  the  force  of  the  gust  diminishes,  and  the 
wind  seems  to  blow  towards  him  from  the  direction  B.  He  ac- 
cordingly turns  toward  it  again,  rising  from  the  ground  till  his 
velocity  relative  to  the  air  has  assumed  its  former  value,  and  he 
moves  horizontally,  turning  again  at  right  angles  to  the  line 
AB,  and  the  cycle  is  completed.  He  thus  moves  along  in  the 
direction  AB  with  a mean  velocity  equal  to  that  of  the  wind, 
rising  when  moving  parallel  to  it,  and  moving  horizontally,  or 
perhaps  slowly  falling,  if  the  gusts  do  not  come  with  sufficient 
frequency,  when  moving  at  right  angles  to  it. 

“ In  the  case  of  all  soaring  birds,  the  spread  tail,  being  an  in- 
clined curved  surface,  presents  a large  area  to  the  wind.  As  it 
is  situated  at  a considerable  distance  from  the  bird’s  centre  of 
gravity,  it  must  convert  him  into  a sort  of  floating  weather-cock, 
the  wings  serving  as  dampers  to  restrain  him  from  turning  too 
quickly.  It  therefore  appears,  if  soaring  really  does  depend  on 
the  interaction  of  varying  wind-currents,  as  if  the  changes  of 
direction  involved  must  be  almost  automatic,  and  not  a thing 
which  the  bird  is  required  to  learn ; although  he  may  doubtless 
learn  to  take  advantage  of  favoring  currents  by  giving  proper 
inclinations  to  his  wings  and  tail. 

“ If  the  question  be  raised  as  to  the  sufficiency  of  the  var^dng 
intensity  of  the  wind-currents  to  maintain  the  bird’s  initial  ve- 
locity against  the  resistance  of  the  air,  we  must  reply  that  it  is 
a matter  which  can  only  be  determined  conclusively  by  experi- 
ment. Certain  it  is,  however,  that  in  windy  weather  the  wind 
does  come  in  gusts.  If  in  the  course  of  his  circles  the  bird  hap- 
pens to  be  travelling  at  right  angles  to  the  wind,  when  the  gust 
strikes  him  he  will  surely  be  turned  round,  almost  in  spite  of 
himself,  so  as  to  face  the  gust.  If  the  bird  does  face  the  gust, 
it  will  certainly  raise  him  to  a higher  level. 


HOW  A BIRD  SOARS. 


87 


“ If  this  explanation  proves  to  be  the  true  one,  the  reason  why 
small  birds  cannot  soar  is  probably,  that,  in  those  of  them  that 
have  suitably  shaped  wings  and  bodies,  their  surfaces  are  so 
large  in  proportion  to  their  weights  that  they  rapidly  assume  the 
velocity  of  the  surrounding  air.  In  order  that  they  might  soar 
to  advantage,  the  gusts  should  come  more  frequently,  and  be  of 
shorter  duration,  than  we  actually  find  to  occur  in  nature.” 

Obviously,  if  the  mean  velocity  of  the  wind  is  high,  and  the 
gusts  comparatively  insignificant,  the  bird  may  rise  without  dif- 
ficulty, but  he  will  drift  rapidly  along  in  the  direction  towards 
which  the  wind  is  blowing.  Let  us  now  imagine  the  conditions 
reversed ; let  the  mean  velocity  of  the  wind  be  very  low,  while 
the  gusts  are  of  great  intensity.  The  bird  will  now  rise  rapidly, 
and  may  then  take  advantage  of  his  position  to  soar  downwards 
against  the  wind,  not  merely  holding  his  own,  but  even  advanc- 
ing against  it.  We  thus  see  how  it  would  be  theoretically  possi- 
ble upon  a windy  day  for  a bird  to  travel  at  will  in  any  desired 
direction  without  making  the  slightest  mechanical  exertion 
whatever,  and  also  without  taking  advantage  of  any  upward 
currents  that  might  exist.  That  these  currents  do  exist  in  cer- 
tain localities,  especially  in  hilly  districts,  and  that  they  are 
often  used  by  the  birds  almost  like  stairways  there  now  seems 
no  reason  to  doubt.  That  such  upward  currents  are  not  abso- 
lutely necessary,  however,  for  purposes  of  soaring,  it  is  the 
object  of  this  article  to  point  out. 


Soon  shall  thy  arm,  unconquered  steam,  afar 
Drag  the  slow  barge,  or  drive  the  rapid  car- 
Or  on  wide  waving  wings  expanded  bear 
The  flying  chariot  through  the  field  of  air. 

— Erasmus  Darwin,  d.  1802. 


[From  Aero.  Ann.,  1896.] 

NATURAL  AND  ARTIFICIAL  FLIGHT. 

By  Hiram  S.  Maxim. 


I. 

INTRODUCTORY. 

At  the  time  I commenced  my  experiments  in  aeronautics  it 
was  not  generally  believed  that  ‘ it  would  ever  be  possible  to 
make  a large  machine  heavier  than  the  air  that  would  lift  itself 
from  the  earth  by  dynamic  energy  generated  by  the  machine  it- 
self. It  is  true  that  a great  number  of  experiments  had  been 
made  with  balloons,  but  these  are  in  no  sense  true  flying  ma- 
chines. Every  one  who  attempted  a solution  of  the  question  by 
machines  heavier  than  the  air,  was  looked  upon  in  very  much 
the  same  light  as  the  man  is  now  who  attempts  to  construct  a 
perpetual  motion  machine.  Up  to  within  a few  years,  nearly 
all  experiments  in  aerial  navigation  by  flying  machines  have 
been  made  by  men  not  versed  in  science,  and  who  for  the  most 
part  have  been  ignorant  of  the  most  rudimentary  laws  of  dy- 
namics. It  is  only  quite  recently  that  scientific  engineers  have 

(88) 


NATURAL  AND  ARTIFICIAL  FLIGHT. 


89 


taken  up  the  question  and  removed  it  from  the  hands  of  charla- 
tans and  mountebanks.  A few  years  ago  many  engineers  would 
not  have  dared  to  face  the  ridicule  which  they  would  be  liable 
to  receive  if  they  had  asserted  that  it  would  be  possible  to  make 
a machine  that  would  lift  itself  by  mechanical  means  into  the 
air.  However,  thanks  to  the  admirable  work  of  Professor 
Langley,  Professor  Thurston,  Mr.  Chanute  and  others,  one  may 
now  express  his  opinion  freely  on  this  subject  and  speculate  as 
to  the  possibilities  of  making  flying  machines,  without  being 
relegated  to  the  realm  of  cranks  and  fanatics. 

During  the  last  five  years  I have  had  occasion  to  write  a large 
number  of  articles  for  the  public  press  on  this  subject,  and  I 
have  always  attempted,  as  far  as  it  is  in  my  power,  to  discuss 
the  subject  in  such  a manner  as  to  be  easily  understood  by  the 
unscientific,  and  I believe  that  my  efforts  have  done  something 
in  the  direction  of  popularizing  the  idea  that  it  is  possible  to 
construct  practical  flying  machines. 

In  preparing  my  present  work,  I have  aimed  as  far  as 
possible  to  discuss  the  question  in  plain  and  simple  language, 
and  to  abstain  from  the  use  of  any  formulae  which  may  not 
be  understood  by  every  one.  It  has  been  my  experience  that 
if  a work  abounds  in  formulae  and  tables,  even  only  a few  of 
the  scientific  will  take  the  trouble  to  read  or  understand  it. 
I have  therefore  confined  myself  to  a plain  statement  of  the 
actual  facts,  describing  the  character  of  my  observations  and 
experiments,  and  giving  the  results  of  the  same.  All  experi- 
ments made  by  others  in  the  same  direction  have  been  on  a 
very  small  scale,  and,  as  a rule,  the  apparatus  employed  has 
been  made  to  travel  around  a circle,  the  size  of  which  has  not 
been  great  enough  to  prevent  the  apparatus  continually  en- 
countering air  which  had  been  influenced  in  some  way  by  the 
previous  revolution. 

The  first  experiments  which  I conducted  were  with  an  appa- 
ratus which  travelled  around  a circle  200  feet  in  circumference, 
and  by  mounting  some  delicate  anemometers  directly  under 
the  path  of  the  apparatus  I ascertained  that  after  it  had  been 
travelling  at  a high  velocity  for  a few  seconds,  there  was  a well- 


90 


THE  AERONAUTICAL  ANNUAL. 


defined  air  current  blowing  downward  around  the  whole  circle, 
so  that  my  planes  in  passing  forward  must  have  been  influenced 
and  their  lifting  effect  reduced  to  some  extent  by  this  down- 
ward current.  My  late  experiments  are  the  first  which  have 
ever  been  made  with  an  apparatus  on  a large  scale  moving  in  a 
straight  line.  In  discussing  the  question  of  aerial  flight  with 
Professor  Langley  before  my  large  experiments  had  been  made, 
the  Professor  suggested  that  there  might  be  some  unknown  fac- 
tor relating  to  size  only  which  might  defeat  my  experiments, 
and  that  none  of  our  experiments  had  at  that  time  been  on  a 
sufficiently  large  scale  to  demonstrate  what  the  lifting  effect  of 
very  large  planes  would  be.  A flying  machine  to  be  of  any 
value  must  of  necessity  be  large  enough  to  carry  at  least  one 
man,  and  the  larger  the  machine  the  smaller  the  factor  of  the 
man’s  weight.  Moreover,  it  is  possible  to  make  engines  of  say 
from  200  to  400  horse-power,  lighter  per  unit  of  power  than 
very  small  engines  of  from  one  to  two  horse-power.  On  the 
other  hand,  it  is  not  advisable  to  construct  a machine  on  too 
large  a scale,  because  as  the  machine  becomes  larger  the  rela- 
tive strength  of  the  material  becomes  less.  In  first  designing 
my  large  machine  I intended  that  it  should  weigh  about  5,000 
pounds  without  men,  water,  or  fuel,  that  the  screw  thrust  should 
be  1,500  pounds,  and  that  the  total  area  of  the  planes  should 
be  5,000  square  feet.  I expected  to  lift  this  machine  and  drive 
it  through  the  air  at  a velocity  of  35  miles  an  hour  with  an 
expenditure  of  about  250  horse-power.  However,  upon  com- 
pleting the  machine  I found  that  many  parts  were  too  weak,  and 
these  had  to  be  supplanted  by  thicker  and  stronger  material. 
This  increased  the  weight  of  the  machine  about  2,000  pounds. 
Upon  trying  my  engines  I found  that  if  required  they  would  de- 
velop 360  horse-power,  and  that  a screw  thrust  of  over  2,000 
pounds  could  be  easily  attained , but  as  an  offset  against  this, 
the  amount  of  power  required  for  driving  the  machine  through 
the  air  was  a good  deal  more  than  I had  anticipated. 

Note.  — For  Mr.  Maxim’s  description  of  this  machine  see  “ Centur)’ Magazine," 
N.Y.,  January,  1895. 


GROVER  C.  BERCDOLL 

NATURAL  AND  ARTIFICIAL  FLIGHT.  91 


II. 


NATURAL  FLIGHT. 

During  the  last  50  years  a great  deal  has  been  said  and 
written  in  regard  to  the  flight  of  birds.  Perhaps  no  other 
natural  phenomenon  has  excited  so  much  interest  and  has  been 
so  little  understood.  Learned  treatises  have  been  written  to 
prove  that  a bird  is  able  to  develop  from  10  to  100 
times  as  much  power  for  its  weight  as  other  animals,  while 
other  equally  learned  treatises  have  shown  most  conclusively 
that  no  greater  amount  of  energy  is  exerted  by  a bird  in  flying 
than  by  land  animals  in  running  or  jumping. 

There  is  no  question  but  what  a bird  has  a higher  physical 
development,  as  far  as  the  generation  of  power  is  concerned, 
than  any  other  animal  we  know  of.  Nevertheless,  I think  that 
every  one  who  has  made  a study  of  the  question  will  agree  that 
some  animals,  such  as  rabbits,  exert  quite  as  much  power  in 
running  in  proportion  to  their  weight  as  a sea-gull  or  an  eagle 
exerts  in  flying. 

The  amount  of  power  which  a land  animal  has  to  exert  is 
always  a fixed  and  definite  quantity.  If  an  animal  weighing 
100  pounds  has  to  ascend  a hill  100  feet  high,  it  always  means 
the  development  of  10,000  foot-pounds.  With  a bird,  how- 
ever, there  is  no  such  thing  as  a fixed  quantity,  because  the 
medium  in  which  the  bird  is  moving  is  never  stationary.  If  a 
bird  weighing  100  pounds  should  raise  itself  into  the  air  100 
feet  during  a perfect  calm,  the  amount  of  energy  developed 
would  be  10,000  foot-pounds  plus  the  slip  of  the  wings.  But, 
as  a matter  of  fact,  the  air  in  which  a bird  flies  is  never  station- 
ary, as  I propose  to  show;  it  is  always  moving  either  up  or 
down,  and  soaring  birds,  by  a very  delicate  sense  of  feeling, 
always  take  advantage  of  a rising  column  of  air.  If  a bird  finds 
itself  in  a column  of  air  which  is  descending,  it  is  necessary  for 
it  to  work  its  wings  very  rapidly  in  order  to  prevent  a descent 
to  the  earth. 

I have  often  observed  the  flight  of  hawks  and  eagles.  They 


92 


THE  AERONAUTICAL  ANNUAL. 


seem  to  glide  through  the  air  with  hardly  any  movement  of 
their  wings.  Sometimes,  however,  they  stop  and  hold  them- 
selves in  a stationary  position  directly  over  a certain  spot,  care- 
fully watching  something  on  the  earth  immediately  below.  In 
such  cases  they  often  work  their  wings  with  great  rapidity, 
evidently  expending  an  enormous  amount  of  energy.  When, 
however,  they  cease  to  hover  and  commence  to  move  again 
through  the  air,  they  appear  to  keep  themselves  at  the  same 
height  with  an  almost  imperceptible  expenditure  of  force. 

Many  unscientific  observers  of  the  flight  of  birds  have  im- 
agined that  a wind  or  a horizontal  movement  of  the  air  is  all 
that  is  necessary  in  order  to  sustain  the  weight  of  a bird  in  the 
air  after  the  manner  of  a kite.  If,  however,  the  wind,  which  is 
only  air  in  motion,  should  be  blowing  everywhere  at  exactly 
the  same  speed  and  in  the  same  direction  (horizontally),  it 
would  offer  no  more  sustaining  power  to  a bird  than  a dead 
calm,  because  there  is  nothing  to  prevent  the  body  of  the  bird 
being  blown  along  with  the  air,  and  whenever  it  had  attained 
the  same  velocity  as  the  air,  no  possible  arrangement  of  the 
wings  would  prevent  it  from  falling  to  the  earth. 

The  wind,  however,  seldom  or  never  blows  in  a horizontal 
direction.  Some  experimenters  have  lately  asserted  that  if  it 
were  possible  for  us  to  ascend  far  enough,  we  should  find  the 
temperature  constantly  falling  until  at  about  20  or  25  miles 
above  the  earth’s  surface  the  absolute  zero  might  be  reached. 
Now,  as  the  air  near  the  earth  never  falls  in  temperature  to 
anything  like  the  absolute  zero,  it  follows  that  there  is  a con- 
stant change  going  on,  the  relatively  warm  air  near  the  surface 
of  the  earth  always  ascending,  and,  in  some  cases,  doing  suffi- 
cient work  in  expanding  to  render  a portion  of  the  water  it 
contains  visible,  forming  clouds,  rain,  or  snow,  while  the  verj^ 
cold  air  is  constantly  descending  to  take  the  place  of  the  rising 
column  of  warm  air. 

On  one  occasion  while  crossing  the  Atlantic  in  fine  weather, 
I noticed,  some  miles  directly  ahead  of  the  ship,  a long  line  of 
glassy  water.  Small  waves  indicated  that  the  wind  was  blowing 
in  the  exact  direction  in  which  the  ship  was  movdng,  and  I 


NATURAL  AND  ARTIFICIAL  FLIGHT. 


93 


observed  as  we  approached  the  glassy  line  that  the  waves  became 
smaller  and  smaller  until  they  completely  disappeared  in  a 
mirror-like  surface  which  was  about  300  or  400  feet  wide  and 
extended  both  to  the  port  and  starboard  in  approximately  a 
straight  line  as  far  as  the  eye  could  reach.  After  passing  the 
centre  of  this  zone,  I noticed  that  small  waves  began  to  show 
themselves,  but  in  the  exact  opposite  direction  to  those  through 
which  we  had  already  passed.  I observed  that  these  waves 
became  larger  and  larger  for  nearly  an  hour.  Then  they  be- 
gan to  get  gradually  smaller,  when  I observed  another  glassy 
line  directly  ahead  of  the  ship.  As  we  approached  it  the  waves 
completely  disappeared,  but  after  passing  through  it  I noticed 
that  the  wind  was  blowing  in  the  opposite  direction  and  that 
the  waves  increased  in  size  exactly  in  the  same  manner  that 
they  had  diminished  on  the  opposite  side  of  the  glassy  zone. 

This  would  seem  to  indicate  that  directly  over  the  centre  of 
the  first  glassy  zone,  the  air  was  meeting  from  both  sides  and 
ascending,  and  that  at  the  other  glassy  zone  the  air  was  de- 
scending in  practically  a straight  line  to  the  surface  of  the 
water  where  it  spread  out  and  set  up  a light  wind  in  both 
directions. 

I spent  the  winter  of  1890-91  on  the  Riviera,  between 
Hyeres  les  Palmiers  and  Monte  Carlo.  The  weather  for  the 
most  part  was  very  fine,  and  I often  had  opportunities  of  ob- 
serving the  peculiar  phenomena  which  I had  already  noticed  in 
the  Atlantic,  only  on  a much  smaller  scale.  Whereas,  in  the 
Atlantic,  the  glassy  zones  were  from  5 to  20  miles  apart,  I often 
found  them  not  more  than  500  feet  apart  in  the  bays  of  the 
Mediterranean. 

At  Nice  and  Monte  Carlo  this  phenomenon  was  also  very 
marked.  On  one  occasion,  while  making  observations  from  the 
highest  part  of  the  promontory  of  Monaco  on  a perfectly  calm 
day,  I noticed  that  the  whole  of  the  sea  presented  this  peculiar 
effect  as  far  as  the  eye  could  reach,  and  that  the  lines  which 
marked  the  descending  air  were  never  more  than  a thousand 
feet  from  those  which  marked  the  centre  of  the  ascending  column. 
At  about  3 o’clock  in  the  afternoon,  a large  black  steamer 


94 


THE  AERONAUTICAL  ANNUAL. 


passed  along  the  coast  in  a perfectly  straight  line,  and  I noticed 
that  its  wake  was  at  once  marked  by  a glassy  line  which  in- 
dicated the  centre  of  an  ascending  column.  This  line  remained 
almost  straight  for  two  hours,  when  finally  it  became  crooked 
and  broken.  The  heat  of  the  steamer  had  been  sufficient  to 
determine  this  upward  current  of  air. 

In  1893,  I spent  two  weeks  in  the  Mediterranean,  going  by  a 
slow  steamer  from  Marseilles  to  Constantinople  and  returning, 
and  I had  many  opportunities  of  observing  the  peculiar  phe- 
nomenon which  I have  before  referred  to.  The  steamer  passed 
over  thousands  of  square  miles  of  calm  sea,  the  surface  being 
only  disturbed  by  large  batches  of  small  ripples  separated  from 
each  other  by  glassy  streaks,  and  I found  that  in  no  case  was 
the  wind  blowing  in  the  same  direction  on  both  sides  of  these 
streaks,  every  one  of  them  either  indicating  the  centre  of  an 
ascending  or  a descending  column  of  air. 

If  we  should  investigate  this  phenomenon  in  w'hat  might  be 
called  a dead  calm,  we  should  probably  find  that  the  air  was 
rising  straight  up  over  the  centres  of  some  of  these  streaks,  and 
descending  in  a vertical  line  over  the  centres  of  the  others. 
But,  as  a matter  of  fact,  there  is  no  such  thing  as  a dead  calm. 
The  movement  of  the  air  is  the  resultant  of  more  than  one 
force.  The  air  is  not  only  rising  in  some  places  and  descend- 
ing in  others,  but  at  the  same  time  the  whole  mass  is  mov- 
ing forward  with  more  or  less  rapidity  from  one  part  of  the 
earth  to  another.  So  we  might  consider  that,  instead  of  the  air 
ascending  directly  from  the  relatively  hot  surface  of  the  earth 
and  descending  vertically  in  other  places,  in  reality  it  is  moving 
on  an  incline. 

Suppose  that  the  local  influence  which  causes  the  up  and 
down  motion  of  the  air  should  be  sufficiently  great  to  cause  it 
to  rise  at  the  rate  of  2 miles  an  hour,  and  that  the  wind  at  the 
same  time  should  be  blowing  at  the  rate  of  10  miles  an  hour; 
the  motion  of  the  air  would  then  be  the  resultant  of  these  two 
velocities.  In  other  words,  it  would  be  blowing  up  an  incline 
of  I in  5.  Suppose  now,  that  a bird  should  be  able  to  so  ad- 
just its  wings  that  it  advanced  5 miles  in  falling  i mile  through 


NATURAL  AND  ARTIFICIAL  FLIGHT. 


95 


a perfectly  calm  atmosphere ; it  would  be  able  to  sustain  itself 
in  an  inclined  wind,  such  as  I have  described,  without  any 
movement  at  all  of  its  wings.  If  it  was  able  to  adjust  its  wings 
in  such  a manner  that  it  could  advance  6 miles  by  falling 
through  I mile  of  air,  it  would  then  be  able  to  rise  as  relates  to 
the  earth  while  in  reality  falling  as  relates  to  the  surrounding 
air. 

In  conducting  a series  of  experiments  with  artillery  and  small 
guns  in  a very  large  and  level  field  just  out  of  Madrid,  I often 
observed  the  same  phenomena  as  relates  to  the  wind,  that  I have 
already  spoken  of  as  having  observed  at  sea,  except  that  the 
lines  marking  the  centre  of  an  ascending  or  a descending  col- 
umn of  air  were  not  so  stationary  as  they  were  over  the  water. 
It  was  not  an  uncommon  thing  when  adjusting  the  sights  of  a 
gun  to  fire  at  a target  at  very  long  range,  making  due  allow- 
ances for  the  wind,  to  have  the  wind  change  and  blow  in  the 
opposite  direction  before  the  word  of  command  was  given  to 
fire.  While  conducting  these  experiments,  I often  noticed  the 
flight  of  eagles.  On  one  occasion  a pair  of  eagles  came  into 
sight  on  one  side  of  the  plain,  passed  directly  over  our  heads 
and  disappeared  on  the  opposite  side.  They  were  apparently 
always  at  the  same  height  from  the  earth  and  soared  completely 
across  the  plain  without  once  moving  their  wings.  This  phe- 
nomenon, I think,  can  only  be  accounted  for  on  the  hypothesis 
that  they  were  able  to  feel  out  with  their  wings  an  ascending 
column  of  air,  that  the  centre  of  this  column  of  air  was  approxi- 
mately a straight  line  running  completely  across  the  plain,  that 
they  found  the  ascending  column  to  be  more  than  necessary  to 
sustain  their  weight  in  the  air,  and  that  whereas,  as  relates  to 
the  earth,  they  were  not  falling  at  all,  they  were  really  falling 
some  2 or  3 miles  an  hour  in  the  air  which  supported  them. 

Again,  at  Cadiz  in  Spain,  when  the  wind  was  blowing  in  very 
strongly  from  the  sea,  I noticed  that  the  sea-gulls  always  took 
advantage  of  an  ascending  column  of  air.  As  the  wind  blew 
in  from  the  sea  and  rose  to  pass  over  the  fortifications,  the  sea- 
gulls selected  a place  where  they  could  slide  down  on  the 
ascending  current  of  air,  keeping  themselves  always  approxi- 


96 


THE  AERONAUTICAL  ANNUAL. 


mately  in  the  same  place  without  any  apparent  exertion. 
When,  however,  they  left  this  ascending  column,  I observed 
that  it  was  necessary  for  them  to  work  their  wings  with  great 
vigor  until  they  again  found  the  proper  place  to  encounter  the 
favorable  current. 

I have  often  noticed  sea-gulls  following  a ship.  I have  ob- 
served that  they  are  able  to  follow  the  ship  without  any 
apparent  exertion ; they  simply  balance  themselves  on  an 
ascending  column  of  air  and  seem  to  be  quite  as  much  at  ease 
as  they  would  be  if  they  were  roosting  on  a solid  support.  If, 
however,  they  are  driven  out  of  this  position,  I find  that  they 
generally  have  to  commence  at  once  to  work  their  passage.  If 
anything  is  thrown  overboard  which  is  too  heavy  for  them  to 
lift,  the  ship  soon  leaves  them,  and  in  order  to  catch  up  with  it 
again,  they  move  their  wings  very  much  as  other  birds  do ; but 
when  once  established  in  the  ascending  column  of  air,  they 
manage  to  keep  up  with  the  ship  by  doing  little  or  no  work. 
In  a head  wind  we  find  them  directly  aft  of  the  ship ; if  the 
wind  is  from  the  port  side,  they  may  always  be  found  on  the 
starboard  quarter,  and  vice  versa. 

Every  one  who  has  passed  a winter  on  the  northern  shores  of 
the  Mediterranean  must  have  observed  the  cold  wind  which  is 
generally  called  the  mistral.  One  may  be  out  driving,  the  sun 
may  be  shining  brightly,  and  the  air  be  warm  and  balmy,  when, 
suddenly,  without  any  apparent  cause,  one  finds  himself  in  a 
cold  descending  wind.  This  is  the  much-dreaded  mistral,  and 
if  at  sea,  it  would  be  marked  by  a glassy  line  on  the  surface  of 
the  water.  On  land,  however,  there  is  nothing  to  render  its 
presence  visible.  I have  found  that  the  ascending  column  of 
air  is  always  very  much  warmer  than  the  descending  column, 
and  that  this  action  is  constantly  taking  place  in  a greater  or 
less  degree. 

From  the  foregoing  deductions  I think  we  may  draw  the 
following  conclusions : 

First,  that  there  is  a constant  interchange  of  air  taking  place, 
the  cold  air  descending,  spreading  itself  out  over  the  surface  of 
the  earth,  becoming  warm,  and  ascending  in  other  places. 


NATURAL  AND  ARTIFICIAL  FLIGHT. 


97 


Second  that  the  centres  of  the  two  columns  are  generally- 
separated  from  each  other  by  a distance  which  may  be  from 
500  feet  to  20  miles. 

Third,  that  the  centres  of  greatest  action  are  not  in  spots, 
but  in  lines  which  may  be  approximately  straight  but  generally 
abound  in  many  sinuosities. 

Fourth,  that  this  action  is  constantly  taking  place  over  both 
the  sea  and  the  land,  that  the  soaring  of  birds,  a phenomenon 
which  has  heretofore  been  so  little  understood,  may  be  ac- 
counted for  on  the  hypothesis  that  the  bird  seeks  out  an 
ascending  column  of  air,  and  that,  while  sustaining  itself  at  the 
same  height  in  the  air  without  any  muscular  exertion,  it  is  in 
reality  falling  at  a considerable  speed  through  the  air  that 
surrounds  it. 

It  has  been  supposed  by  some  scientists  that  the  birds  may 
take  advantage  of  some  vibratory  or  rolling  action  of  the  air. 
I find,  however,  from  careful  observation  and  experiment,  that 
the  motion  of  the  wind  is  comparatively  steady,  and  that  the 
short  vibratory  or  rolling  action  is  always  very  near  to  the  earth 
and  is  produced  by  the  air  flowing  over  the  tops  of  hills,  high 
buildings,  or  trees.  If  a kite  is  flown  only  a few  feet  above  the 
ground,  it  will  be  found  that  the  current  of  air  is  very  unsteady. 
If  it  is  allowed  to  mount  to  500  feet,  the  unsteadiness  nearly  all 
disappears,  while  if  it  is  further  allowed  to  mount  to  a height  of 
1,500  or  2,000  feet,  the  pull  on  the  cord  is  almost  constant,  and, 
if  the  kite  is  well  made,  it  remains  practically  stationary  in  the 
air. 

I have  often  noticed  in  high  winds,  that  light  and  fleecy  clouds 
come  into  view,  say,  about  2,000  feet  above  the  surface  of  the 
earth,  and  that  they  pass  rapidly  and  steadily  by,  preserving 
their  shape  completely.  This  would  certainly  indicate  that 
there  is  no  rapid  local  disturbance  in  the  air  in  their  immediate 
vicinity,  but  that  the  whole  mass  of  air  in  which  these  clouds 
are  formed  is  practically  travelling  in  the  same  direction  and  at 
the  same  velocity.  Numerous  aeronauts  have  also  testified  that, 
no  matter  how  hard  the  wind  may  be  blowing,  the  balloon  is 
always  practically  in  a dead  calm,  and  if  a piece  of  gold-leaf  is 


98 


THE  AERONAUTICAL  ANNUAL. 


thrown  overboard  even  in  a gale,  the  gold-leaf  and  the  balloon 
never  part  company  in  a horizontal  direction,  though  they  may 
in  a vertical  direction. 

Birds  may  be  divided  into  two  classes  : first,  the  soaring  birds, 
which  practically  live  upon  the  wing,  and  which,  by  some  very 
delicate  sense  of  touch,  are  able  to  feel  the  exact  condition  of 
the  air.  Many  fish  which  live  near  the  top  of  the  water  are 
greatly  distressed  by  sinking  too  deeply,  while  others  which  live 
at  great  depths  are  almost  instantly  killed  by  being  raised  to 
the  surface.  The  swim  bladder  of  a fish  is  in  reality  a deli- 
cate barometer  provided  with  sensitive  nerves  which  enable  the 
fish  to  feel  whether  it  is  sinking  or  rising  in  the  water.  With 
the  surface  fish,  if  the  pressure  becomes  too  great,  the  fish  in- 
voluntarily exerts  itself  to  rise  nearer  the  surface  and  so  diminish 
the  pressure,  and  I have  no  doubt  that  the  air-cells,  which  are 
known  to  be  very  numerous  and  to  abound  throughout  the 
bodies  of  birds,  are  so  sensitive  as  to  enable  soaring  birds  to 
know  at  once  whether  they  are  in  an  ascending  or  a descending 
column  of  air. 

The  other  class  of  birds  consists  of  those  which  only  employ 
their  wings  for  the  purpose  of  taking  them  rapidly  from  one 
place  to  another.  Such  birds  may  be  considered  not  to  expend 
their  power  so  economically  as  the  soaring  birds.  They  do  not 
spend  a very  large  portion  of  their  time  in  the  air,  but  what 
time  they  are  on  the  wing  they  exert  an  immense  amount  of 
power  and  fly  very  rapidly,  generally  in  a straight  line,  taking 
no  advantage  of  air  currents.  Partridges,  pheasants,  wild  ducks, 
geese,  and  some  birds  of  passage  may  be  taken  as  types  of  this 
kind.  This  class  of  birds  has  relatively  small  wings,  and  carries 
about  times  as  much  weight  per  square  foot  of  surface  as 
soaring  birds  do. 

III. 

ARTIFICIAL  FLIGHT.  — THE  ENGINES. 

There  is  no  question  but  what  birds  — and,  for  that  matter, 
all  animals  — when  considered  as  thermo-dynamic  machines. 


NATURAL  AND  ARTIFICIAL  FLIGHT. 


99 


are  very  perfect  motors ; they  develop  the  full  theoretical 
amount  of  energy  in  the  carbon  consumed.  This  we  are  quite 
unable  to  do  with  any  artificial  machine,  but  birds  for  the  most 
part  have  to  content  themselves  with  food  which  is  not  very  rich 
in  carbon.  It  is  quite  true  that  a bird  may  develop  from  lo 
to  15  times  as  much  power  from  the  carbon  consumed  as  may 
be  developed  by  the  best  steam-engine,  but  as  an  offset  against 
this,  a steam-engine  is  able  to  consume  petroleum,  which  has 
at  least  20  times  as  many  thermal  units  per  pound  as  the  ordi- 
nary food  of  birds.  The  movement  of  a bird’s  wings,  from  long 
years  of  development,  has  without  doubt  attained  a great 
degree  of  perfection.  Birds  are  able  to  scull  themselves 
through  the  air  with  very  little  loss  of  energy.  To  imitate  by 
mechanical  means  the  exact  and  delicate  motion  of  their  wings 
would  certainly  be  a very  difficult  task,  and  I do  not  believe 
that  we  should  attempt  it  in  constructing  an  artificial  flying 
machine.  In  Nature  it  is  necessary  that  an  animal  should  be 
made  all  in  one  piece.  It  is  therefore  quite  out  of  the  question 
that  any  part  or  parts  should  revolve.  For  land  animals  there 
is  no  question  but  what  legs  are  the  most  perfect  system  possi- 
ble, but  in  terrestrial  locomotion  by  machinery  — not  necessarily 
in  one  piece  — the  wheel  is  found  to  be  much  more  effective 
and  efficient.  The  swiftest  animal  can  only  travel  for  a minute 
of  time  at  half  the  speed  of  a locomotive,  while  the  locomotive 
is  able  to  maintain  its  much  greater  speed  for  many  hours  at  a 
time.  The  largest  land  animals  only  weigh  about  5 tons,  while 
the  largest  locomotives  weigh  from  60  to  80  tons.  In  the  sea, 
the  largest  animal  weighs  about  75  tons,  while  the  ordinary 
Atlantic  liner  weighs  from  4,000  to  14,000  tons.  The  whale  no 
doubt  is  able  to  maintain  a high  speed  for  several  hours  at  a 
time,  but  the  modern  steamer  is  able  to  maintain  a still  higher 
speed  for  many  consecutive  days. 

As  artificial  machines  for  terrestrial  and  aquatic  locomotion 
have  been  made  immensely  stronger  and  larger  than  land  or 
water  animals,  so,  in  a flying  machine,  it  will  be  necessary  to 
construct  it  much  heavier  and  stronger  than  the  largest  bird. 
If  one  should  attempt  to  propel  such  a machine  with  wings,  it 


lOO 


THE  AERONAUTICAL  ANNUAL. 


would  be  quite  as  difficult  a problem  to  solve  as  it  would  be  to 
make  a locomotive  that  would  walk  on  legs.  What  is  required 
in  a flying  machine  is  something  to  which  a very  large  amount 
of  power  can  be  directly  and  continuously  applied  without 
any  intervening  levers  or  joints,  and  this  we  find  in  the  screw 
propeller. 

It  was  about  20  years  ago  that  I first  commenced  to  think  of 
the  question  of  artificial  flight.  My  first  idea  was  to  construct 
a machine  with  two  large  screws  on  vertical  shafts.  I proposed 
to  run  these  screws  in  reverse  directions  by  the  use  of  a caloric 
or  hot-air  engine,  but  after  considering  the  subject  for  some 
time,  I came  to  the  conclusion  that  this  class  of  engine  would 
not  do.  When  the  Brayton  gas  engine  first  made  its  appear- 
ance, I commenced  drawings  of  a machine,  using  a modification 
of  the  Brayton  motor  which  I designed  expressly  for  the  pur- 
pose ; but  even  this  was  found  to  be  too  heavy,  and  it  was  not 
until  after  I abandoned  the  vertical  screw  system  that  it  was 
possible  for  me  to  design  a machine  which  in  theory  ought 
to  fly. 

The  next  machine  which  I considered  was  on  the  kite  or 
aeroplane  system.  This  was  also  to  be  driven  by  an  oil  engine. 
Oil  engines  at  that  time  were  not  so  simple  as  now,  and  more- 
over the  system  of  ignition  was  very  heavy,  cumbersome,  and 
uncertain.  Since  that  time,  however,  gas  and  oil  engines  have 
been  very  much  improved,  and  the  ignition  tube,  which  is 
almost  universally  used,  has  greatly  simplified  the  ignition,  so 
that  at  the  present  time  I am  of  the  opinion  that  an  oil  engine 
might  be  designed  which  would  be  suitable  for  the  purpose. 


IV. 


THE  ADVANTAGES  AND  DISADVANTAGES  OF  VERY  NARROW 

PLANES. 

My  experiments  have  demonstrated  that  relatively  narrow 
aeroplanes  lift  more  per  square  foot  than  very  wide  ones,  but  as 
an  aeroplane,  no  matter  how  narrow  it  may  be,  must  of  neces- 


NATURAL  AND  ARTIFICIAL  FLIGHT. 


lOI 


sity  have  some  thickness,  it  is  not  advantageous  to  place  them 
too  near  together.  Suppose  that  aeroplanes  should  be  made 
\ in.  thick  and  be  superposed  3 inches  apart,  that  is,  at  a pitch 
of  3 inches.  One- 
twelfth  part  of  the  whole 
space  through  which 
these  planes  would  have 
to  be  driven  would  be 
occupied  by  the  planes 
themselves,  and  eleven- 
twelfths  would  be  air 
space  (Fig.  i).  If  a 
group  of  planes  thus 
mounted  should  be  driv- 
en through  the  air  at 
the  rate  of  36  miles  an 
hour,*  the  air  would 
have  to  be  driven  for- 
ward at  the  rate  of  3 
miles  an  hour,  or  else 
it  would  have  to  be  compressed,  or  spun  out,  and  pass  be- 
tween the  spaces  at  a speed  of  39  miles  an  hour.  As  a 
matter  of  fact,  however,  the  difference  in  pressure  is  so  very 
small,  that  practically  no  atmospheric  compression  takes  place. 
The  air,  therefore,  is  driven  forward  at  the  rate  of  3 miles  an 
hour,  and  this  consumes  a great  deal  of  power,  in  fact,  so  much 
that  there  is  a decided  disadvantage  in  using  narrow  planes  thus 
arranged. 

In  regard  to  the  curvature  of  narrow  aeroplanes,  I have  found 
that  if  one  only  desires  to  lift  a large  load  in  proportion  to  the 
area,  the  planes  may  be  made  very  hollow  on  the  underneath 
side ; but  when  one  considers  the  lift  in  terms  of  screw  thrust, 
I find  it  advisable  that  the  planes  should  be  as  thin  as  possible 
and  the  underneath  side  nearly  flat.  I have  also  found  that  it 
is  a great  advantage  to  arrange  the  planes  after  the  manner 

* The  arrows  in  the  accompanying  drawings  show  the  direction  of  the  air  currents,  the 
experiments  having  been  made  with  stationary  planes  and  a moving  current  of  air. 


102 


THE  AERONAUTICAL  ANNUAL. 


shown  in  Fig.  2.  In  this  manner,  the  sum  of  all  the  spaces 
between  the  planes  is  equal  to  the  whole  area  occupied  by  the 


Fig.  2. 


planes;  consequently,  the  air  neither  has  to  be  compressed, 
spun  out,  or  driven  forward.  I am  therefore  by  this  arrange- 
ment able  to  produce  a large  lifting  effect  per  square  foot, 
and,  at  the  same  time,  to  keep  the  screw  thrust  within  reason- 
able limits. 

A large  number  of  experiments  with  very  narrow  aeroplanes 
have  been  conducted  by  Mr.  Horatio  Phillips  at  Harrow,  in 

England.  Fig.  3 
shows  a cross  section 
of  one  of  Mr.  Phil- 
lips’ planes.  Mr. 
Phillips  is  of  the 
opinion  that  the  air  in  striking  the  top  side  of  the  plane  is 
thrown  upward  in  the  manner  shown  and  a partial  vacuum  is 
thereby  formed  over  the  central  part  of  the  plane,  and  that 
the  lifting  effect  of  planes  made  in  this  form  is  therefore 
very  much  greater  than  with  ordinary  narrow  planes.  I have 
experimented  with  these  “ sustainers  ” (as  Mr.  Phillips  calls 
them)  myself,  and  I find  it  is  quite  true  that  they  lift  in  some 
cases  as  much  as  8 lb.  per  sq.  ft.,^  but  the  lifting  effect  is  not 

1 In  my  early  experiments  I lifted  as  much  as  8 lb.  per  sq.  ft.  with  aeroplanes  which  were 
only  slightly  curved,  but  very  thin  and  sharp. 


Fig.  3. 


NATURAL  AND  ARTIFICIAL  FLIGHT. 


103 


produced  in  the  exact  manner  that  Mr.  Phillips  seems  to  sup- 
pose. The  air  does  not  glance  off  in  the  manner  shown.  As 
the  “ sustainer  ” strikes  the  air,  two  currents  are  formed,  one 
following  the  exact  contour  of  the  top  and  the  other  the  bot- 
tom. These  two  currents  join  and  are  thrown  downward  as 
relates  to  the  “ sustainer  ” at  an  angle  which  is  the  resultant  of 
the  angles  at  which  the  two  currents  meet.  (Fig.  4.)  These 


Fig.  4. 

“ sustainers  ” may  be  made  to  lift  when  the  front  edge  is  lower 
than  the  rear  edge  because  they  encounter  still  air,  and  leave  it 
with  a downward  motion. 

In  my  experiments  with  narrow  superposed  planes,  I have 
always  found  that  with  strips  of  thin  metal  made  sharp  at  both 
edges  and  only  slightly  curved,  the  lifting  effect,  when  con- 
sidered in  terms  of  screw  thrust,  was  always  greater  than  with  any 
arrangement  of  the  wooden  aeroplanes  used  in  Phillips’  experi- 
ments. It  would  therefore  appear  that  there  is  no  advantage  in 
the  peculiar  form  of  “ sustainer  ” employed  by  this  inventor. 

If  an  aeroplane  be  made  perfectly  flat  on  the  bottom  side  and 
convex  on  the  top,  as  shown  in  Fig.  5,  and  be  mounted  in  the 
air  so  that  the  bottom 
side  is  exactly  horizon- 
tal, it  produces  a lifting 
effect  no  matter  in  which  p'g  5- 

direction  it  is  run,  be- 
cause as  it  advances  it  encounters  stationary  air  which  is  divided 
into  two  streams.  The  top  stream  being  unable  to  fly  off  at  a 
tangent  when  turning  over  the  top  curve,  flows  down  the  incline 
and  joins  the  current  which  is  flowing  over  the  lower  horizontal 
surface.  The  angle  at  which  the  combined  stream  of  air  leaves 
the  plane  is  the  resultant  of  these  two  angles ; consequently,  as 
the  plane  finds  the  air  in  a stationary  condition  and  leaves  it 
with  a downward  motion,  the  plane  itself  must  be  lifted.  It  is 


104 


THE  AERONAUTICAL  ANNUAL. 


true  that  small  and  narrow  aeroplanes  may  be  made  to  lift  con- 
siderably more  per  square  foot  of  surface  than  very  large  ones, 
but  they  do  not  offer  the  same  safeguard  against  a rapid  descent 
to  the  earth  in  case  of  a stoppage  or  breakdown  of  the  machin- 
ery. With  a large  aeroplane  properly  adjusted,  a rapid  and 
destructive  fall  to  the  earth  is  quite  impossible. 

In  the  foregoing  experiments  with  narrow  aeroplanes,  I 
employed  an  apparatus  which  enabled  me  to  mount  my 
planes  at  any  angle  in  a powerful  blast  of  air,  and  to  weigh  the 
exact  lifting  effect  and  also  the  tendency  to  drift  with  the  wind. 
This  apparatus  also  enables  me  to  determine  with  a great 
degree  of  nicety  the  best  form  of  an  atmospheric  condenser  to 
employ. 


V. 

THE  EFFICIENCY  OF  SCREW  PROPELLERS.  — STEERING, 
STABILITY,  ETC. 

Before  I commenced  my  experiments  at  Baldwjm’s  Park,  I 
attempted  to  obtain  some  information  in  regard  to  the  action  of 
screw  propellers  working  in  the  air.  I went  to  Paris  and  saw 
the  apparatus  which  the  French  Government  employed  for  test- 
ing the  efficiency  of  screw  propellers,  but  the  propellers  were  so 
very  badly  made  that  the  experiments  were  of  no  value.  Upon 
consulting  an  English  experimenter  who  had  made  a “ lifelong 
study”  of  the  question,  he  assured  me  that  I should  find  the 
screw  propeller  very  inefficient  and  very  wasteful  of  power.  He 
said  that  all  screw  propellers  had  a powerful  fan-blower  action, 
drawing  in  air  at  the  centre  and  discharging  it  with  great  force 
at  the  periphery.  I found  that  no  two  men  were  agreed  as  to 
the  action  of  screw  propellers.  All  the  data  or  formulae  avail- 
able were  so  confusing  and  contradictory  as  to  be  of  no  value 
whatsoever.  Some  experimenters  were  of  the  opinion  that  in 
computing  the  thrust  of  a screw  we  should  only  consider  the 
projected  area  of  the  blades,  and  that  the  thrust  would  be  equal 


K 


J 


I 


Plate  XV. 


H G fed 

A group,  showing  the  various  forms  of  screws  which  Mr.  Maxim  has  tested.  The  screw  J was 
found  to  be  the  most  efficient.  A similar  screw  K,  with  wider  blades,  did  not  do  so  well.  The  screw  E, 
although  very  light  and  small,  did  very  well.  G,  a screw  made  on  the  French  plan,  proved  the  worst  screw 
experimented  with.  H,  the  same  form  as  J,  except  that  the  blades  are  much  thicker,  also  did  remarkably  well. 


THE  FORWARD  RUDDER  FOR  STEERING  MR.  MAXIM’S  MACHINE  IN  A 
VERTICAL  DIRECTION. 

This  plate  is  especially  interesting  as  showing  the  construction  of  the  framing.  — Ed. 


NATURAL  AND  ARTIFICIAL  FLIGHT. 


105 


to  a wind  blowing  against  a normal  plane  of  equal  area  at  a 
velocity  equal  to  the  slip.  Others  were  of  the  opinion  that  the 
whole  screw  disk  would  have  to  be  considered ; that  is,  that  the 
thrust  would  be  equal  to  a wind  blowing  against  a normal  plane 
equal  to  the  area  of  the  whole  disk  at  the  velocity  of  the  slip. 
The  projected  area  of  the  two  screw  blades  of  my  machine  is  94 
square  feet,  and  the  area  of  the  2 screw  disks  is  500  square  feet. 
According  to  the  first  system  of  reasoning,  therefore,  the  screw 
thrust  of  my  large  machine,  when  running  at  40  miles  an  hour 
with  a slip  of  18  miles  per  hour,  would  have  been,  according  to 
the  well-known  formula,  X .005=? 

18^  X .005  X 94  = 152.28  pounds. 

If,  however,  we  should  have  considered  the  whole  screw  disk,  it 
would  have  been  — 

18^  X -005  X 500  = 810  pounds. 

However,  when  the  machine  was  run  over  the  track  at  this  rate, 
the  thrust  was  found  to  be  rather  more  than  2,000  lbs.  When 
the  machine  was  secured  to  the  track  and  the  screws  revolved 
until  the  pitch  in  feet  multiplied  by  the  turns  per  minute  was 
equal  to  68  miles  an  hour,  it  was  found  that  the  screw  thrust 
was  2,164  lbs.  In  this  case  it  was  of  course  all  slip,  and  when 
the  screws  had  been  making  a few  turns  they  had  established  a 
well-defined  air-current,  and  the  power  exerted  by  the  engines 
was  simply  to  maintain  this  air-current,  and  it  is  interesting  to 
note  that  if  we  compute  the  projected  area  of  these  blades  by 
the  foregoing  formula,  the  thrust  would  be  — 

68^  X .005  X 94  — 2173.28  pounds, 
which  is  almost  exactly  the  observed  screw  thrust.  From  this,  it 
would  appear  when  the  machine  is  stationary,  and  all  the  power  is 
consumed  in  slip,  that  only  the  projected  area  of  the  screw  blades 
should  be  considered.  But  whenever  the  machine  is  allowed  to 
advance,  and  to  encounter  new  air,  the  inertia  of  which  has  not 
been  disturbed,  the  efficiency  increases  in  geometricalprogression. 
The  exact  rate  for  all  speeds  I have  not  yet  ascertained.  My  ex- 
periments have,  however,  shown  that  with  a speed  of  40  miles 
an  hour  and  a screw  slip  of  18  miles  an  hour,  a well-made  screw 


io6 


THE  AERONAUTICAL  ANNUAL. 


propeller  is  13.1  times  as  efficient  as  early  experimenters  had 
supposed  and  attempted  to  prove  by  elaborate  formulae. 

When  I first  commenced  my  experiments  with  a large  ma- 
chine, I did  not  know  exactly  what  form  of  boiler,  gas  genera- 
tor, or  burner  I should  finally  adopt;  I did  not  know  the  exact 
size  that  it  would  be  necessary  to  make  my  engines ; I did  not 
know  the  size,  the  pitch,  or  the  diameter  of  the  screws  which 
would  be  the  most  advantageous.  Neither  did  I know  the  form 
of  aeroplane  which  I should  finally  adopt.  It  was  therefore 
necessary  for  me  to  make  the  foundation  or  platform  of  my  ma- 
chine of  such  a character  that  it  would  allow  me  to  make  the 
modifications  necessary  to  arrive  at  the  best  results.  The  plat- 
form of  the  machine  is  therefore  rather  larger  than  is  necessary, 
and  I find  if  I were  to  design  a completely  new  machine,  that  it 
would  be  possible  to  greatly  reduce  the  weight  of  the  frame- 
work, and,  what  is  still  more,  to  greatly  reduce  the  force  neces- 
sary to  drive  it  through  the  air. 

At  the  present  time,  the  body  of  my  machine  ‘ is  a large  plat- 
form, about  8 ft.  wide  and  40  ft.  long.  Each  side  is  formed  of 
very  strong  trusses  of  steel  tubes,  braced  in  every  direction  by 
strong  steel  wires.  The  trusses  which  give  stiffness  to  this 
superstructure  are  all  below  the  platform.  In  designing  a new 
machine,  I should  make  the  trusses  much  deeper  and  at  the 
same  time  very  much  lighter,  and,  instead  of  having  them  below 
the  platform  on  which  the  boiler  is  situated,  I should  have  them 
constructed  in  such  a manner  as  to  completely  enclose  the 
boiler  and  the  greater  part  of  the  machinery.  I should  make 
the  cross-section  of  the  framework  rectangular,  and  pointed 
at  each  end.  I should  cover  the  outside  very  carefully  with 
balloon  material,  giving  it  a perfectly  smooth  and  even  surface 
throughout,  so  that  it  might  be  easily  driven  through  the  air. 

In  regard  to  the  screws,  I am  at  the  present  time  able  to 
mount  screws  17  ft.  10  in.  in  diameter.  I find,  however,  that  my 
machine  would  be  much  more  efficient  if  the  screws  were  24 
feet  in  diameter,  and  I believe  with  such  very  large  screws,  four 
blades  would  be  much  more  efficient  than  two. 

iSee  A New  Flying  Machine,  by  H.  S.  Maxim.  Century  Magazine,  N.  Y.,  January, 
1895.  — 


NATURAL  AND  ARTIFICIAL  FLIGHT. 


107 


My  machine  may  be  steered  to  the  right  or  to  the  left  by 
running  one  of  the  propellers  faster  than  the  other.  Very  con- 
venient throttle  valves  have  been  provided  to  facilitate  this 
system  of  steering.  An  ordinary  vertical  rudder  placed  just 
after  the  screws  may,  however,  prove  more  convenient,  if  not 
more  efficient. 

The  machine  is  provided  with  fore  and  aft  horizontal  rudders, 
both  of  which  are  connected  with  the  same  windlass.  If  the 
forward  rudder  is  placed  at  an  angle  considerably  greater  than 
that  of  the  main  aero- 
plane, and  the  rear  rud- 
der placed  flat  so  as  not 
to  lift  at  all  (Fig.  7),  and 
the  machine  run  over  the 

track  at  a high  speed,  the  Fig.  7.  — The  forward  wheels  off  the  track. 

front  wheels  will  be  lifted 

from  the  steel  rails,  leaving  the  rear  wheels  on  the  rails.  If  the 
rudders  are  placed  in  the  reverse  position  so  that  the  front  rudder 

is  thrown  out  of  action,  and 
the  rear  rudder  lifts  to  its  full 
extent  (Fig.  8),  the  hind 
wheels  will  be  lifted  from 
the  steel  rails,  leaving  only 

Fig.  8.  — The  rear  wheels  off  the  track.  the  forward  wheels  toucllingf. 

o 

If  both  rudders  are  placed 
at  such  an  angle  that  they  both  lift  (Fig.  9),  and  the  ma- 
chine is  run  at  a very  high  velocity,  all  four  of  the  wheels 
will  be  lifted  from  the  steel 
rails.  This  would  seem  to 
show  that  these  rudders  are 
efficient  as  far  as  vertical 
steering  is  concerned.  If 
the  machine  should  break  Fig.  9.  — aii  the  wheels  off  the  track, 
down  in  the  air  it  would  be 

necessary  to  tilt  the  rudders  in  the  position  shown  in  Fig.  10, 
when  it  would  fall  to  the  ground  without  pitching  or  diving. 

In  regard  to  the  stability  of  the  machine,  the  centre  of  weight 


io8 


THE  AERONAUTICAL  ANNUAL. 


is  much  below  the  centre  of  lifting  effect ; moreover,  the  upper 
wings  are  set  at  such  an  angle  that  whenever  the  machine  tilts 
to  the  right  or  to  the  left, 
the  lifting  effect  is  increased 
on  the  lower  side  and  dimin- 
ished on  the  higher  side 
(Fig.  il).  This  simple  ar- 
rangement makes  the  ma-  Fig.  lO.  — showing:  the  manner  of  placing  the 

- fore  and  aft  rudders  in  case  of  a breakage 

chine  automatic  as  lar  as  of  the  machinery, 
rolling  is  concerned.  I am 

of  the  opinion  that  whenever  flying  machines  come  into  use  it 
will  be  necessary  to  steer  them  in  a vertical  direction  by  means 

of  an  automatic  steering 
gear  controlled  by  a gyro- 
scope. It  will  certainly  not  be 
more  difficult  to  manoeuvre 
and  steer  such  machines  than 
it  is  to  control  completely 
submerged  torpedoes. 

When  the  machine  is  once 
perfected,  it  will  not  require 
a railway  track  to  enable  it 
to  get  the  necessary  velocity 
Fig.  II.  to  rise.  A short  run  over  a 

moderately  level  field  will 
suffice.  As  far  as  landing  is  concerned,  the  aerial  navigator 
will  touch  the  ground  while  moving  forward,  and  the  ma- 
chine will  be  brought  to  a state  of  rest  by  sliding  on  the 
ground  for  a short  distance.  In  this  manner  very  little  shock 
will  result,  whereas  if  the  machine  is  stopped  in  the  air  and 
allowed  to  fall  directly  to  the  earth  without  advancing,  the 
shock,  although  not  strong  enough  to  be  dangerous  to  life  or 
limb,  might  be  sufficient  to  disarrange  or  injure  the  machinery. 


NATURAL  AND  ARTIFICIAL  FLIGHT. 


109 


VI. 

THE  COMPARATIVE  VALUE  OF  DIFFERENT  MOTORS. 

So  far  I have  only  discussed  the  navigation  of  the  air  by  the 
use  of  propellers  driven  by  a steam  engine.  The  engines  that  I 
employ  are  what  are  known  as  compound  engines,  that  is,  they 
have  a large  and  a small  cylinder.  Steam  at  a very  high  pres- 
sure enters  the  high  pressure  cylinder,  expands  and  escapes  at 
a lower  pressure  into  a larger  cylinder  where  it  again  expands 
and  does  more  work.  A compound  engine  is  more  economical 
in  steam  than  a simple  engine,  and  therefore  requires  a smaller 
boiler  to  develop  the  same  horse-power,  so  that  when  we  con- 
sider the  weight  of  water  and  fuel  for  a given  time,  together  with 
the  weight  of  the  boiler  and  the  engine,  the  complete  motor 
with  a compound  engine  is  lighter  than  a simple  engine.  How- 
ever, if  only  the  weight  of  the  engine  is  to  be  considered,  then 
the  simple  engine  will  develop  more  power  per  unit  of  weight 
than  the  compound  engine.  For  instance,  if  instead  of  allowing 
the  steam  to  enter  the  small  cylinder,  and  the  exhaust  from  this 
cylinder  to  enter  the  large  or  low-pressure  cylinder,  which  neces- 
sitates that  the  high-pressure  piston  has  to  work  against  a back- 
pressure equal  to  the  full  pressure  in  the  low-pressure  cylinder, 
I should  connect  both  cylinders  direct  with  the  live  steam  and 
allow  both  to  discharge  their  exhaust  directly  into  the  air.  I 
should  then  have  a pair  of  simple  engines,  and  instead  of  develop- 
363  horse-power,  they  would  develop  fully  500  horse-power, 
or  nearly  l horse-power  for  every  pound  of  their  weight.  I 
mention  this  fact  to  show  that  the  engines  are  exceedingly  light, 
and  that  when  compared  with  simple  engines  their  power  should 
be  computed  on  the  same  basis.  It  will  therefore  be  seen  that  if 
we  do  not  take  into  consideration  the  steam  supply  or  the  amount 
of  fuel  and  water  necessary,  the  simple  steam  engine  is  an  ex- 
ceedingly light  motor. 

But  as  before  stated,  great  improvements  have  recently  been 
made  in  oil  engines.  I have  thought  much  on  this  subject,  and 
am  of  the  opinion  that  if  one  had  an  unlimited  supply  of  money. 


no 


THE  AERONAUTICAL  ANNUAL. 


a series  of  experiments  could  be  very  profitably  conducted  with 
a view  of  adapting  the  oil  engine  for  use  on  flying  machines.  If 
we  use  a steam  engine  it  is  necessary  to  have  a boiler,  and  at 
the  best  a boiler  is  rather  a large  and  heavy  object  to  drive 
through  the  air.  If  we  use  an  oil  engine  no  boiler  is  necessary 
and  the  amount  of  heat  carried  over  in  the  cooling  water  will 
only  be  one-seventh  part  of  what  is  carried  over  in  the  exhaust 
from  a steam  engine  of  the  same  power.  Therefore  the  con- 
denser need  only  be  one-seventh  part  of  the  size,  and  conse- 
quently could  be  made  lighter  with  the  tubes  placed  at  a greater 
distance  apart,  and  thus  reduce  the  amount  of  power  necessary 
to  drive  the  machine  through  the  air.  Moreover,  the  supply  of 
water  necessary  will  be  greatly  reduced  and  a cheaper  and 
heavier  oil  may  be  employed  which  is  not  so  liable  to  take  fire 
in  case  of  an  accident.  It  is,  then,  only  a question  as  to  whether 
an  oil  engine  can  be  made  so  light  as  to  keep  its  weight  within 
that  of  a steam  motor;  that  is,  an  oil-engine  in  order  to  be 
available  for  the  purpose  must  be  as  light,  including  its  water 
supply,  as  a complete  steam  motor  which  includes  not  only  the 
engine,  but  also  the  boiler,  the  feed-pumps,  the  water  supply, 
the  burner,  the  gas  generator,  and  six-sevenths  of  the  condenser. 
It  requires  a very  perfect  steam-engine  and  boiler,  not  using  a 
vacuum,  to  develop  a horse-power  with  a consumption  of 
pounds  of  petroleum  per  hour;  but  there  are  many  oil  engines 
which  develop  a horse-power  with  rather  less  than  one  pound 
of  oil  per  hour.  It  will  therefore  be  seen  that  as  far  as  fuel  is 
concerned  the  oil  engine  has  a decided  advantage  over  the  more 
complicated  steam  motor.  Moreover,  with  an  oil  engine  the 
cooling  water  is  not  under  pressure,  so  that  the  waste  of  water 
would  be  much  less  than  with  a steam  engine,  where  the  pres- 
sure is  so  high  as  to  cause  a considerable  amount  of  waste 
through  joints,  valves,  and  numerous  stuffing  boxes. 

The  great  advances  that  have  been  made  of  late  years  in 
electrical  science  and  engineering  have  led  many  to  believe  that 
almost  any  knotty  scientific  question  could  be  solved  by  the 
employment  of  electrical  agencies,  and  a great  deal  has  been 


GROVER  C.  BERGDOLL 


NATURAL  AND  ARTIFICIAL  FLIGHT.  Ill 

written  and  said  in  regard  to  navigating  the  air  by  flying 
machines  driven  by  electric  motors. 

Before  I commenced  my  experiments  I made  inquiries  of 
all  the  prominent  electrical  engineering  establishments  where 
there  was  any  likelihood  of  obtaining  light  and  efficient  electric 
motors,  and  I found  that  it  was  impossible  to  obtain  one  that 
would  develop  a horse-power  for  any  considerable  time  that 
would  weigh  less  than  150  lbs.  Since  that  time,  notwithstand- 
ing that  a great  deal  has  appeared  in  the  public  prints  about 
the  efficiency  and  lightness  of  electric  motors,  I am  unable  to 
learn  of  any  concern  that  is  ready  to  furnish  a complete  motor, 
including  a primary  or  secondary  battery  which  would  supply 
the  necessary  current  for  two  hours  at  a time,  at  a weight  of 
less  than  150  lbs.  per  horse-power,  and  as  far  as  I have  been 
able  to  ascertain  from  what  I have  myself  seen,  I cannot  learn 
that  there  are  any  motors  in  practical  use  which  do  not  weigh, 
including  their  storage  batteries,  at  least  300  lbs.  per  horse- 
power. The  last  electric  motor  which  I examined  was  in  a 
boat ; it  was  driven  by  a primary  battery  which  weighed  over 
1,000  lbs.  to  the  horse-power.  From  this  I am  of  the  opinion 
that  we  can  not  at  present  look  to  electricity  with  any  hope 
of  finding  a motor  which  is  suitable  for  the  purpose  of  aerial 
navigation. 


VII. 

CONCLUSION. 

My  large  machine,  which  was  injured  in  my  late  experiments, 
has  now  been  repaired  and  improved,  and  is  quite  ready  to  be 
used  in  any  other  experiments  which  I may  wish  to  make  on 
the  limited  area  which  I now  have  at  my  disposal.  The  rail- 
way track  on  which  my  experiments  have  been  made  is  1,800 
feet  long  and  the  land  on  all  sides  is  thickly  studded  with 
large  trees.  When  making  experiments  about  500  feet  of  the 
track  is  used  in  getting  up  the  necessary  speed  and  300  feet  is 


1 12 


THE  AERONAUTICAL  ANNUAL. 


utilized  in  bringing  the  machine  again  to  a state  of  rest.  My 
clear  run  is  therefore  limited  to  i,ooo  feet,  and  the  time  which 
the  machine  takes  to  pass  over  this  length  of  rail  is  at  the  most 
only  a few  seconds.  It  will  therefore  be  seen  that  it  is  not  an 
easy  matter  to  conduct  experiments  in  a satisfactory  manner. 
In  addition  to  these  experiments  with  a large  machine,  I am 
also  conducting  a series  of  experiments  in  a blast  of  air  issuing 
from  a trunk  3 feet  square.  The  air  is  set  in  motion  by  the 
action  of  screw  propellers  driven  by  a steam  engine  of  60 
horse-power,  and  I am  able  to  obtain  any  atmospheric  velocity 
that  I require,  from  5 to  90  miles  an  hour.  This  apparatus 
is  shown  in  Fig.  6,  and  is  constructed  in  such  a manner  that 
it  enables  me  to  mount  in  this  current  of  air  any  object  that  I 
wish  to  experiment  with.  For  instance,  a bar  of  wood  3 inches 
square  is  mounted  in  the  blast  of  air  so  that  one  of  its  sides 
forms  a normal  plane  perpendicular  to  the  direction  of  the 
blast.  The  engine  is  then  run  until  the  air  is  passing  through 
the  trunk  at  a velocity  of  50  miles  an  hour.  The  tendency  of 
this  bar  of  wood  to  travel  in  the  direction  of  the  air  may  then 
be  accurately  determined,  and  this  is  considered  as  unity.  A 
cylinder  exactly  3 inches  in  diameter  may  then  be  mounted 
and  tested  in  the  same  manner.  The  cylinder  will  of  course 
have  less  tendency  to  travel  with  the  air  than  the  square  bar  of 
wood,  and  whatever  this  tendency  is,  will  be  the  coefficient  of 
a cylinder.  I have  provided  oval,  elliptical,  and  various  other 
shaped  objects  to  be  experimented  with,  and  when  the  experi- 
ments are  finished  I shall  know  the  exact  coefficient  of  all 
shapes  that  it  may  be  practical  to  use  in  the  framework  of  a 
flying  machine,  and  also  what  effect  is  produced  by  placing 
two  or  more  bodies  in  close  proximity  to  each  other. 

In  addition  to  these  experiments,  I am  also  able  with  the 
same  air  blast  to  ascertain  the  efficiency  of  various  forms  of 
aeroplanes,  superposed  or  otherwise,  and  placed  at  all  angles, 
the  apparatus  being  provided  with  a scale  beam  which  not  only 
enables  me  to  measure  the  drift,  but  also  to  accurately  weigh 
the  lifting  effect.  The  aeroplane,  or  grouping  of  aeroplanes,  in 


NATURAL  AND  ARTIFICIAL  FLIGHT.  II3 

which  the  drift  will  go  the  greatest  number  of  times  into  the 
lift  will  be  considered  the  most  satisfactory  for  the  purpose. 

Experiments  are  also  being  made  in  the  same  air  blast  with 
a view  of  ascertaining  the  condensing  and  lifting  power  of 
various  forms  of  tubes,  steam  in  the  condition  of  exhaust  being 
passed  through  the  tubes  while  the  air  is  driven  between  them 
at  any  velocity  required.  The  experiments  are  being  made 
with  pure  steam  and  also  with  steam  contaminated  with  oil, 
with  a view  of  ascertaining  to  what  extent  the  efficiency  of  the 
condenser  is  reduced  by  a film  of  oil  such  as  may  be  expected 
from  exhaust  steam.  These  experiments  will  enable  me  to 
ascertain  very  exactly  the  weight  and  the  efficiency  of  atmos- 
pheric condensers,  the  amount  that  their  tubes  may  be  made  to 
lift  at  various  speeds  and  atmospheric  conditions,  and  will  also 
enable  me  to  select  the  form  which  I find  most  suitable  for  the 
purpose. 

In  navigating  a boat,  it  is  only  necessary  that  one  should  be 
able  to  turn  it  to  the  right  or  to  the  left  (port  or  starboard), 
but  with  a flying  machine  it  is  not  only  necessary  to  steer  it  to 
the  right  or  left  (horizontally),  but  also  in  a vertical  direction 
to  prevent  it  from  rearing  up  forward  or  pitching,  and  this,  if 
it  is  accomplished  by  hand,  will  require  the  constant  vigilance 
of  a man  at  the  wheel  who  can  make  observations,  think,  and 
act  instantly.  In  order  to  prevent  a too  rapid  up  and  down 
deviation  of  the  machine  I have  constructed  it  of  great  length, 
so  that  the  man  at  the  helm  will  have  more  time  to  think  and 
act.  As  before  stated,  however,  I am  of  the  opinion  that  the 
steering  in  a vertical  direction  should  be  automatically  con- 
trolled by  a gyroscope,  and  I have  made  an  apparatus  which 
consists  of  a steam  piston  acting  directly  upon  the  fore  and  aft 
rudders,  the  steam  valve  being  controlled  by  a gyroscope.  As 
the  rudders  are  moved  by  the  steam,  their  movement  shuts  the 
steam  off  in  exactly  the  same  manner  that  the  moving  of  a 
rudder  shuts  off  the  steam  in  the  well-known  steam-steering 
apparatus  now  universally  in  use  on  all  large  steamers. 

Now  that  it  is  definitely  known  that  it  is  possible  to  construct 
a large  machine  which  is  light  enough  and  at  the  same  time 


1 14  the  aeronautical  annual. 

powerful  enough  to  raise  its  own  weight  and  that  of  its  engi- 
neers into  the  air,  the  next  question  which  presents  itself  for 
solution  is  to  ascertain  how  to  steer  and  control  such  a machine 
when  actually  free  from  the  earth.  When  it  is  considered  that 
the  machine  is  of  great  size  and  that  it  is  necessary  that 
it  should  move  through  the  air  at  a velocity  of  at  least  35 
miles  an  hour  in  order  to  leave  the  ground,  it  will  be  obvi- 
ous that  manoeuvring  experiments  cannot  be  conducted  in  a 
circumscribed  place  such  as  I now  have.  It  is  therefore 
necessary  for  me  to  obtain  new  and  much  larger  premises 
where  I shall  have  a very  large  and  level  field  at  my  disposal. 
It  is  not  an  easy  matter  to  obtain  a field  of  this  character  in 
England,  and  it  is  almost  impossible  to  find  a suitable  place 
near  London.  Moreover,  experiments  of  this  character,  which 
are  of  little  value  unless  conducted  on  a large  scale,  are  ex- 
ceedingly expensive,  in  fact,  too  expensive  to  be  conducted  by 
private  individuals.  Nevertheless,  as  my  experiments  have 
shown  most  conclusively  that  flying  machines  are  not  only 
possible  but  practicable,  I think  I am  justified  in  continuing  my 
experiments  until  a comparatively  perfect  flying  machine  has 
been  evolved.  When  I have  obtained  possession  of  a suitable 
field,  I propose  to  erect  a large  building  which  will  contain  the 
machine  with  all  its  wings  in  position.  The  building  which  I 
have  at  present,  notwithstanding  that  it  cost  $15,000,  is  not 
large  enough  for  the  purpose,  as  the  wings  all  have  to  be  taken 
off  before  the  machine  can  be  housed. 

There  are  so  many  points  that  may  be  improved  that  I have 
determined  to  build  a new  machine  on  a somewhat  smaller  scale, 
using  about  200  or  250  horse-power.  I shall  make  the  engines 
of  a longer  stroke  in  proportion  to  their  diameter  so  as  to  get  a 
greater  piston  speed.®  I shall  construct  my  screw  propellers 
with  4 long  and  narrow  blades,  very  sharp  and  thin,  and  shall 
make  them  large  enough  so  that  the  pressure  on  the  projected 
area  of  the  blades  will  be  about  10  lbs.  per  square  foot  in- 
stead of  over  20  lbs.  as  now.  This  will  greatly  reduce  the 

^ The  present  piston  speed  does  not  exceed  800  feet  per  minute.  The  piston  speed  of 
express  locomotives  is  often  more  than  1,000  feet  per  minute. 


NATURAL  AND  ARTIFICIAL  FLIGHT.  I 1 5 

waste  of  power  which  is  now  lost  in  screw  slip.  As  the  present 
boiler  has  been  found  larger  than  is  necessary,  my  next  boiler 
will  be  made  lighter  and  smaller,  and  instead  of  carrying  a pres- 
sure of  320  lbs.  to  the  square  inch,  I shall  only  carry  275 
lbs.  But  the  greatest  improvement  will  be  made  in  the 
framework  of  the  machine,  which  will  be  constructed  with  a 
view  of  enabling  everything  to  be  driven  through  the  air  with 
the  least  possible  resistance.  The  main  aeroplane  will  be  the 
same  form  as  now,  but  placed  at  an  angle  of  i in  13  instead  of 
I in  8,  and  will  be  used  principally  for  preventing  the  machine 
from  accidentally  falling  to  the  earth.  The  principal  lifting 
effect  will  be  derived  from  a considerable  number  of  relatively 
narrow  aeroplanes  placed  on  each  side  of  the  machine  and 
mounted  in  such  a position  that  the  air  can  pass  freely  between 
them.  The  fore  and  aft  rudders  will  be  the  same  form  as  those 
now  employed.  The  condenser  will  consist  of  a large  number 
of  small  hollow  aeroplanes  about  2 inches  wide,  made  of  very 
thin  and  light  metal  and  placed  immediately  behind  the  screw- 
propellers.  They  will  be  placed  at  such  an  angle  as  to  lift 
about  1,000  pounds  in  addition  to  their  weight  and  the  weight 
of  their  contents.  Instead  of  mounting  my  machine  as  now  on 
4 wheels,  I propose  to  mount  it  on  3,  the  two  hind  wheels  being 
about  40  feet  apart  and  the  forward  wheel  placed  about  60  feet 
in  front  of  these.  I propose  to  lay  down  a track  of  3 rails,  the 
sleepers  being  embedded  in  the  ground  so  as  to  produce  a com- 
paratively level  surface.  This  railway  track  should  be  oval  or 
circular  in  form  so  that  the  machine  may  be  heavily  weighed  to 
keep  it  on  the  track  and  be  run  at  a high  speed.  This  will 
enable  me  to  test  the  furnace  draught,  the  burner,  the  steam, 
the  boiler,  the  engines,  the  propelling  effects  of  the  screws,  and 
the  efficiency  of  the  condenser  while  the  machine  is  on  the 
ground. 

When  all  the  machinery  has  been  made  to  run  smoothly  I 
shall  remove  all  the  weight  except  that  directly  over  the  front 
wheel,  and  shall  place  a device  between  the  wheel  and  the 
machine  that  will  indicate  the  lift  on  the  front  end  of  the 
machine.  I shall  then  run  the  machine  over  the  track  at  a 


ii6  the  aeronautical  annual. 

velocity  which  will  just  barely  lift  the  hind  wheels  off  the  track, 
leaving  the  front  wheel  on  the  track.  If  the  rear  end  of  the 
machine  lifts  into  the  air  it  will  change  the  angle  of  the  planes 
and  the  lifting  effect  will  be  correspondingly  diminished.  This 
will  prevent  rising  too  high.  Special  wheels  with  a wide  face 
suitable  for  running  on  either  the  rails  or  the  earth  will  be  pro- 
vided for  the  purpose,  and  when  I find  that  I can  keep  the  hind 
wheels  in  the  air  and  produce  a varying  lifting  effect  above  and 
below  the  normal  weight  resting  on  the  front  wheel,  I shall  re- 
move the  weight  from  the  forward  wheel  and  attempt  free  flight 
by  running  the  machine  as  near  the  ground  as  possible,  making 
the  first  attempt  by  running  against  the  wind,  and  it  will  only 
be  after  I find  that  I can  steer  my  machine  and  manage  it 
within  a few  feet  of  the  earth,  ascend  and  descend  again  at  will, 
that  I shall  attempt  high  flight. 

My  experiments  have  certainly  demonstrated  that  a steam 
engine  and  boiler  may  be  made  which  will  generate  a horse- 
power for  every  six  pounds  of  weight,  and  that  the  whole  motor, 
including  the  gas  generator,  the  water  supply,  the  condenser, 
and  the  pumps  may  be  all  made  to  come  inside  of  1 1 lbs. 
to  the  horse-power.  They  also  show  that  well  made  screw  pro- 
pellers working  in  the  air  are  fairly  efficient,  and  that  they 
obtain  a sufficient  grip  upon  the  air  to  drive  the  machine  for- 
ward at  a high  velocity ; that  very  large  aeroplanes,  if  well  made 
and  placed  at  a proper  angle,  will  lift  as  much  as  2^  lbs.  per 
square  foot  at  a velocity  not  greater  than  40  miles  an  hour; 
also  that  it  is  possible  for  a machine  to  be  made  so  light  and  at 
the  same  time  so  powerful  that  it  will  lift  not  only  its  owm  weight 
but  a considerable  amount  besides,  with  no  other  energy  except 
that  derived  from  its  own  engines.  Therefore  there  can  be  no 
question  but  what  a flying  machine  is  now  possible  without  the 
aid  of  a balloon  in  any  form. 

In  order  to  obtain  these  results  it  has  been  necessary  for  me 
to  make  a great  number  of  expensive  experiments  and  to  care- 
fully study  many  of  the  properties  of  the  air.  Both  Lord 
Kelvin  and  Lord  Rayleigh,  after  witnessing  a series  of  my  ex- 
periments, expressed  themselves  as  of  the  opinion  that  all  the 


Teceiu  experrmenxs  writ  x>e  aX)ie  tO  COnstfiTct  a practical  flying 
machine  which  cannot  fail  to  be  a great  advantage  to  mankind. 

The  numerous  and  very  expensive  experiments,  conducted 
on  an  unprecedented  scale,  which  have  made  all  this  possible, 
and  also  brought  to  light  new  laws  relating  to  the  atmosphere, 
cannot  fail  to  be  of  the  greatest  value  to  mankind,  and  it  is  on 
this  basis  that  I submit  the  foregoing  thesis. 


[From  Aero.  Ann.,  1697-j 


GLIDING  EXPERIMENTS. 


By  Percy  S.  Pilcher. 

Experimental  Departme?it  of  Hiram  S.  Maxim. 


I MADE  my  first  trials  with  a soaring  machine  in  the  summer 
of ’95,  having  constructed  the  machine  during  the  spring. 

I had  seen  photographs  of  Lilienthal’s  apparatus,  but  I pur- 
posely made  mine  before  going  to  see  his  so  that  I should  not 
copy  his  details.  I,  however,  went  to  see  him  fly  before  I com- 
menced to  experiment  myself.  My  first  machine  had  150  square 
feet  of  surface  and  the  wing  tips  were  considerably  raised  above 
the  body.  At  first  I had  a vertical  rudder  only,  but  I soon  dis- 
covered that  I could  do  absolutely  nothing  without  a horizontal 
rudder.  I found  that  it  was  quite  impossible  to  control  the 
pitching  motions  of  the  machine,  and  it  was  not  until  I had  put 
on  the  horizontal  rudder  that  I was  able  to  leave  the  ground  at 
all.  This  point  is  very  clearly  illustrated  by  experiments  with 
model  gliders.  It  is  exceedingly  difficult  to  make  a glider  with 

(u8) 


GLIDING  EXPERIMENTS. 


I19 

one  surface  only  which  will  sail  properly,  but  with  two  surfaces 
nothing  is  easier. 

Although  a machine  in  which  the  wing  tips  are  considerably 
raised  would  always  tend  to  right  itself  when  falling,  it  is  almost 
impossible  to  use  such  a machine  for  practising  soaring  out  of 
doors,  because  although  the  machine  is  stable  enough  when  the 
wind  is  right  ahead,  if  the  wind  shifts  and  gets  a little  on  the 
side  it  will  press  the  weather  wing  up  and  depress  the  lee  one 
so  as  to  turn  the  machine  over.  But  when  I altered  the  shape 
of  the  wings  so  that  they  rose  in  the  centre,  but  turned  down 
again  towards  the  tips,  that  is,  so  that  the  tips  were  scarcely 
higher  than  the  middle  of  the  machine,  the  machine  became 
comparatively  easy  to  handle,  and  I was  able  for  a beginner  to 
make  some  very  good  jumps.  On  one  occasion  when  a man 
towed  the  machine  by  a string  attached  to  the  front  of  the 
machine  I spent  seventeen  seconds  in  the  air,  and  this  is  the 
longest  time  I have  ever  been  off  the  ground. 

During  the  summer  I made  a second  machine  which  was 
straight  transversely,  although  curved  in  the  fore  and  aft  direc- 
tion. All  the  wing  surface  was  considerably  raised  so  that  it 
was  just  above  my  head  when  I was  in  the  machine,  but  with 
this  machine  I could  not  get  along  at  all.  When  the  weather 
became  too  cold  I had  to  stop  experimenting,  and  during  the 
winter  I built  a new  machine,  which  has  170  square  feet  of  sur- 
face and  weighs  50  pounds. 

During  the  last  summer  I had  to  be  very  busy  about  other 
things,  so  that  I have  only  had  the  machine  out  about  ten  times 
and  have  not  been  able  to  choose  my  days.  In  this  machine 
I did  away  with  the  vertical  rudder  altogether.  For  days  when 
there  is  not  much  wind  the  machine  is  quite  manageable  as  it 
is,  but  for  squally  days  I think  that  a vertical  rudder  should  be 
added.  With  this  machine  I have  twice  cleared  nearly  100 
yards,  once  with  a slight  side  wind  and  once  in  a dead  calm. 
Most  unfortunately  I have  never  had  the  machine  out  when 
there  has  been  a breeze  blowing  up  the  best  hill  for  experi- 
menting, or  I should  be  able  to  give  a much  better  account  of 
its  performances.  Once  when  sailing  fast  I saw  I was  going 
to  land  in  a big  bush,  so  getting  back  a little  in  the  machine  I 
was  able  to  rise  a little  and  pass  quite  clear  of  the  bush, 
although  it  was  quite  calm  at  the  time ; and  I have  also  been 
able  to  steer  sideways  to  a limited  extent  by  moving  the  weight 
of  my  body  towards  the  side  to  which  I wanted  the  machine  to 
turn.  This  is  the  first  machine  in  which  I have  had  any  wheels, 


120 


THE  AERONAUTICAL  ANNUAL. 


which  are  a great  convenience  for  moving  the  machine  about, 
and  often  save  the  framework  from  getting  broken  if  one  lands 
clumsily.  The  wheels  are  backed  by  stiff  springs  which  can 
absorb  a considerable  blow. 

A new  machine  is  being  built  which  will  have  an  oil  engine 
to  drive  a screw-propeller.  With  this  machine,  without  the 
engine,  I drop  50  feet  in  10  seconds;  that  is  at  the  rate  of  300 
feet  per  minute  ; taking  my  weight  and  the  weight  of  the  machine 
at  220  pounds  the  work  lost  per  minute  will  be  about  66,000 
foot-pounds  or  2-horse  power.  When  I have  been  flown  as  a 
kite  it  seems  that  about  30  pounds  pull  will  keep  me  floating  at 
a speed  of  about  2,200  feet  per  minute,  or  25  miles  an  hour. 
30  X 2,200  ==  66,000  foot-pounds  = 2-horse  power,  which 
comes  to  just  the  same  thing. 

An  engine  is  now  being  made  which  will,  I hope,  exert  enough 
power  to  overcome  the  losses  arising  from  friction  and  slip, 
and  keep  the  new  machine  floating  horizontally.  Of  course 
for  the  same  wing-surface  the  machine  will  have  to  sail  faster 
in  order  to  keep  afloat  with  the  extra  weight  of  the  engine,  and 
more  power  than  the  2-horse  power  will  therefore  have  to  be 
used. 

About  170  square  feet  seems  to  be  the  best  area  for  a 
machine  of  this  class  for  a man  of  average  weight ; if  it  is  made 
larger  the  machine  becomes  heavier,  and  is  much  more  difficult 
to  handle  because  of  its  increased  size  and  weight,  and  if  it  is 
smaller  its  sailing  speed  becomes  unpleasantly  great. 

Last  June  I happened  to  be  in  Berlin  again,  and  Herr  Lilien- 
thal  very  kindly  allowed  me  to  fly  off  his  hill  with  one  of  his 
double  surface  machines.  A light  steady  breeze  was  blowing, 
and  after  the  practice  I had  had  with  my  own  I had  no  difficulty 
in  handling  his  machine,  but  I was  very  much  afraid  that  with 
the  superposed  wings  high  above  the  machine,  as  shown  in  Lilien- 
thal’s  latest  machine,  they  would  prove  very  dangerous  machines, 
especially  in  squally  weather. 

I hope  with  the  new  machine  with  the  engine  that  I shall  be 
able  to  obtain  results  worth  reporting  in  your  next  ANNUAL,  but 
“ we  shall  see  what  we  shall  see.” 

On  Sept.  30,  1899,  Mr.  Pilcher  met  with  a fatal  accident  while  experi- 
menting near  Rugby,  England. 


[From  Aero.  Ann.,  1895.] 


WISE  UPON  HENSON. 


The  machine  shown  in  the  accompanying  plate  was  patented 
by  Mr.  Henson  in  England  in  1842. 

Mr.  John  Wise,  in  his  book  entitled  “ A System  of  Aeronaut- 
ics ” (Phila.,  1850),  writes  concerning  it  as  follows; 

“ The  next  which  is  worthy  of  consideration  we  find  in 
Henson’s  idea.  Many  persons  in  England  were  sanguine  in 
the  belief  that  his  machine  was  destined  to  perfect  the  art  of 
aerial  navigation,  and  it  was  seriously  contemplated  to  build 
one  after  his  model,  with  which  to  cross  the  Atlantic.  Indeed, 
it  was  well  calculated  to  inspire  such  a belief  in  the  mere 
theoretical  mind,  but  to  the  practical  man  it  at  once  occurs. 
What  is  to  keep  it  from  tilting  over  in  losing  its  balance  by  a 
flaw  of  wind,  or  any  other  casualty,  and  thus  tumbling  to  the 
ground,  admitting  that  it  could  raise  itself  up  and  move  for- 
ward ? 

“ The  principal  feature  of  the  invention  is  the  very  great  ex- 
panse of  its  sustaining  planes,  which  are  larger,  in  proportion 
to  the  weight  it  has  to  carry,  than  those  of  many  birds ; but  if 
they  had  been  still  greater,  they  would  not  have  sufficed  of  them- 
selves to  sustain  their  own  weight,  to  say  nothing  of  their  ma- 
chinery and  cargo  ; surely,  though  slowly,  they  would  have  come 
to  the  ground.  The  machine  advances  with  its  front  edge  a 
little  raised ; the  effect  of  which  is  to  present  its  under  surface 
to  the  air  over  which  it  is  passing,  the  resistance  of  which,  act- 
ing on  it  like  a strong  wind  on  the  sails  of  a windmill,  prevents 
the  descent  of  the  machine  and  its  burden.  The  sustaining  of 
the  whole,  therefore,  depends  upon  the  speed  at  which  it  is 
travelling  through  the  air,  and  the  angle  at  which  its  under 
surface  impinges  on  the  air  in  its  front ; and  this  is  exactly  the 

(I2I) 


122 


■ THE  AERONAUTICAL  ANNUAL. 


principle  by  which  birds  are  upheld  in  their  flight  with  but 
slight  motion  of  their  wings,  and  often  with  none. 

“ But,  then,  this  result,  after  the  start,  depends  entirely  on  keep- 
ing up  the  speed,  and  there  remains  beyond  that,  the  still  more 
formidable  difflculty  of  first  obtaining  that  speed.  All  former 
attempts  of  this  kind  have  failed,  because  no  engine  existed  that 
was  at  once  light  enough  and  powerful  enough  to  lift  even  its 
own  weight  through  the  air  with  the  necessary  rapidity.  Mr. 
Henson  has  removed  this  difflculty,  partly  by  inventing  a steam- 
engine  of  extreme  lightness  and  efficiency,  and  partly  by  another 
and  very  singular  device,  which  requires  particular  notice.  The 
machine,  fully  prepared  for  flight,  is  started  from  the  top  of  an 
inclined  plane,  in  descending  which  it  attains  a velocity  neces- 
sary to  sustain  it  in  its  further  progress.  That  velocity  would 
be  gradually  destroyed  by  the  resistance  of  the  air  to  the  for- 
ward flight;  it  is,  therefore,  the  office  of  the  steam-engine  and 
the  vanes  it  actuates  simply  to  repair  the  loss  of  velocity ; it  is 
made,  therefore,  only  of  the  power  and  weight  necessary  for 
that  small  effect.  Here,  we  apprehend,  is  the  chief,  but  not  the 
only  merit  and  originality  of  Mr.  Henson’s  invention ; and  to 
this  happy  thought  we  shall  probably  be  indebted  for  the  first 
successful  attempt  to  traverse  at  will  another  domain  of  nature.” 

In  the  “Popular  Science  Review,”  1869,  Vol.  VIII.,  p.  i, 
Mr.  F.  W.  Brearey  states  that  this  machine  was  never  con- 
structed.^ 

The  account  of  it  is  given  in  this  Annual  partly  because  of 
the  interest  which  attaches  to  Mr.  Henson’s  plans  on  account 
of  their  date,  and  partly  for  the  sake  of  showing  what  Mr.  Wise 
thought  of  the  combination  of  an  aeroplane  with  a steam- 
engine. 

Nine  years  after  the  publication  of  his  book,  Mr.  Wise  with 
John  La  Mountain  made  one  of  the  most  famous  balloon  voy- 
ages on  record.  They  left  St.  Louis  on  July  i,  1859;  “the 
States  of  Illinois  and  Indiana  were  passed  over  in  the  night  and 
Ohio  was  reached  in  the  morning.  The  balloon  then  passed 
across  Lake  Erie  into  New  York,  and  to  Lake  Ontario,  into 


1 See  “ Progress  in  Flying  Machines,"  Chanute,  p.  84. 


HEWSOW’S  NEW  iEEIAE  STEAM  CAMKIACJE, 


Grover  c.  BER«eeifeu 


Descrijitive  text  may  be  found  in  above  issue,  also  in  the  same  paper  Feb.  23,  1S96. 


WISE  UPON  HENSON. 


123 


which  it  descended,  but  rose  again,  and  a landing  was  made  in 
Henderson,  Jefferson  County,  N.Y.  The  time  occupied  in 
making  this  journey  was  nineteen  hours  and  fifty  minutes,  and 
the  distance  traversed  1,150  miles,  or  826  in  an  air  line.”  ^ 

Twenty  years  later,  in  1879,  Mr.  Wise  again  ascended  from 
St.  Louis,  this  time  in  the  “ Pathfinder.”  He  was  last  seen 
to  pass  over  Illinois  in  a northeasterly  direction,  and  is  sup- 
posed to  have  perished  in  Lake  Michigan.  James  Glaisher 
wrote  of  him : “ In  America  Mr.  Wise  is  par  excellence  the 
aeronaut;  he  has  made  several  hundred  ascents,  and  many 
of  them  are  distinguished  for  much  skill  and  daring.  He  also 
appears  to  have  pursued  his  profession  with  more  energy  and 
capacity  than  has  any  other  aeronaut  in  recent  times,  and  his 
‘ History  of  Aerostation  ’ shows  him  to  possess  much  higher 
scientific  attainments  than  balloonists  usually  have.  In  fact, 
Mr.  Wise  stands  alone  in  this  respect,  as  nearly  all  professional 
aeronauts  are  destitute  of  scientific  knowledge.” 

^ Appleton’s  Cyclopaedia  of  American  Biography,  Vol.  III.,  p.  602.  See  also  Vol.  VI., 
p.  581. 


Compiled  from  the  Report  of  the  Chief  of  the  Weather  Bureau,  1891-92. 

MAXIMUM  VELOCITIES  ARE  FOR  A FIVE-MINUTE  PERIOD.  A WIND  VXLOCITy 
OF  40  MILES  PER  HOUR  IS  CONSIDERED  A GALE. 


1 Average  for 
the  year. 

] Miles  per 
hour. 

Maximum 
monthly 
average. 
Miles  per 
hour. 

Minim  um 
monthly 
average. 

Miles  per 
hour. 

Maximum 

velocity. 

Number  of 
days  with 
gales. 

Boston,  Mass 

12.0 

15.9  in  March. 

9.6  in  July. 

48 

8 

Buffalo,  N.Y 

10.9 

13.7  in  December. 

8.4  in  August. 

55 

26 

Chattanooga,  Tenn.  . . . 

S-i 

7.5  in  April. 

3.4  in  September. 

35 

0 

Chicago,  111 

16.8 

22.2  in  April. 

13.2  in  June. 

72 

59 

Cleveland,  0 

1 1. 1 

15.6  in  November. 

8.2  in  March. 

64 

16 

Denver,  Col 

7-4 

9.1  in  April. 

5.3  in  February. 

48 

3 

New  Orleans,  La 

8.8 

12.0  in  April. 

6.0  in  August. 

50 

5 

New  York,  N.Y 

10.8 

14.6  in  March. 

6.9  in  August. 

49 

6 

Pittsburgh,  Pa 

6.5 

84  in  November. 

4.6  in  July. 

38 

0 

Portland,  Me 

8.4 

10.9  in  March. 

7.2  in  August. 

45 

4 

Portland,  Ore 

6.0 

9.2  in  November. 

4.6  in  January. 

41 

2 

St.  Louis,  Mo 

I I.O 

13.4  in  January. 

8.1  in  August. 

48 

13 

San  h'rancisco.  Cal 

8.7 

12.0  in  July. 

4.t  in  January'. 

6 

Savannah,  Ga 

7.8 

9.0  in  April. 

6.2  in  August. 

32 

0 

(J24) 


[From  Aero.  Ann.,  1897.] 


STORY  OF  EXPERIMENTS  IN  MECHANICAL 

FLIGHT. 

By  Samuel  Pierpont  Langley. 


The  Editor  of  “The  Asnual  ” has  asked  me  to  give  matter 
of  a somewhat  personal  nature  for  a narrative  account  of  my 
work  in  aerodromics. 

The  subject  of  flight  interested  me  as  long  ago  as  I can 
remember  anything,  but  it  was  a communication  from  Mr. 
Lancaster,  read  at  the  Buffalo  meeting  of  the  American  Asso- 
ciation for  the  Advancement  of  Science,  in  1886,  which  aroused 
my  then  dormant  attention  to  the  subject.  What  he  said  con- 
tained some  remarkable  but  apparently  mainly  veracious 
observations  on  the  soaring  bird,  and  some  more  or  less  para- 
doxical assertions,  which  caused  his  communication  to  be 
treated  with  less  consideration  than  it  might  otherwise  have 
deserved.  Among  these  latter  was  a statement  that  a 
model,  somewhat  resembling  a soaring  bird,  wholly  inert,  and 
without  any  internal  power,  could,  nevertheless,  under  some 
circumstances  advance  against  the  wind  without  falling;  which 
seemed  to  me  then,  as  it  did  to  members  of  the  Association, 
an  utter  impossibility,  but  which  I have  since  seen  reason  to 
believe  is,  within  limited  conditions,  theoretically  possible. 

I was  then  engaged  in  the  study  of  astro-physics  at  the 
Observatory  in  Allegheny,  Pennsylvania.  The  subject  of 
mechanical  flight  could  not  be  said  at  that  time  to  possess  any 
literature,  unless  it  were  the  publications  of  the  French  and 
English  aeronautical  societies,  but  in  these,  as  in  everything 
then  accessible,  fact  had  not  yet  always  been  discriminated  from 
fancy.  Outside  of  these,  almost  everything  was  even  less  trust- 
worthy; but  though  after  I had  experimentally  demonstrated 

(125) 


126 


THE  AERONAUTICAL  ANNUAL. 


certain  facts,  anticipations  of  them  were  found  by  others  on 
historical  research,  and  though  we  can  now  distinguish  in  retro- 
spective examination  what  would  have  been  useful  to  the  inves- 
tigator if  he  had  known  it  to  be  true,  there  was  no  test  of  the 
kind  to  apply  at  the  time.  I went  to  work,  then,  to  find  out 
for  myself,  and  in  my  own  way,  what  amount  of  mechanical 
power  was  requisite  to  sustain  a given  weight  in  the  air,  and 
make  it  advance  at  a given  speed,  for  this  seemed  to  be  an 
inquiry  which  must  necessarily  precede  any  attempt  at  mechan- 
ical flight,  which  was  the  very  remote  aim  of  my  efforts. 

The  work  was  commenced  in  the  beginning  of  1887  by  the 
construction,  at  Allegheny,  of  a turn-table  of  exceptional  size, 
driven  by  a steam-engine,  and  this  was  used  during  three 
years  in  making  the  “ Experiments  in  Aerodynamics,”  which 
were  published  by  the  Smithsonian  Institution,  under  that  title, 
in  1891.  Nearly  all  the  conclusions  reached  were  the  result 
of  direct  experiment  in  an  investigation  which  aimed  to  take 
nothing  on  trust.  Few  of  them  were  then  familiar,  though  they 
have  since  become  so,  and  in  this  respect  knowledge  has  ad- 
vanced so  rapidly  that  statements  which  were  treated  as  par- 
adoxical on  my  first  enunciation  of  them  are  now  admitted 
truisms. 

It  has  taken  me,  indeed,  but  a few  years  to  pass  through  the 
period  when  the  observer  hears  that  his  alleged  observation 
was  a mistake ; the  period  when  he  is  told  that  if  it  were  true, 
it  would  be  useless ; and  the  period  when  he  is  told  that  it  is 
undoubtedly  true,  but  that  it  has  always  been  known. 

May  I quote  from  the  introduction  to  this  book  what  was 
said  in  1891? 

“ I have  now  been  engaged  since  the  beginning  of  the  year 
1887  in  experiments  on  an  extended  scale  for  determining  the 
possibilities  of,  and  the  conditions  for,  transporting  in  the  air  a 
body  whose  specific  gravity  is  greater  than  that  of  the  air,  and 
I desire  to  repeat  my  conviction  that  the  obstacles  in  its  way 
are  not  such  as  have  been  thought;  that  they  lie  more  in  such 
apparently  secondary  difficulties  as  those  of  guiding  the  body 
so  that  it  may  move  in  the  direction  desired,  and  ascend  or 


Plaie  XVII. 


LANGLEY'S  AERODROME  IN  FLIGHT. 
May  6,  1896. 


1 


EXPERIMENTS  IN  MECHANICAL  FLIGHT. 


127 


descend  with  safety,  than  in  what  may  appear  to  be  the  primary 
difficulties  due  to  the  nature  of  the  air  itself,”  and,  I added,  that 
in  this  field  of  research  I thought  that  we  were,  at  that  time 
(only  six  years  since),  “in  a relatively  less  advanced  condition 
than  the  study  of  steam  was  before  the  time  of  Newcomen.”  It 
was  also  stated  that  the  most  important  inference  from  those 
experiments  as  a whole  was  that  mechanical  flight  was  possible 
with  engines  we  could  then  build,  as  one-horse  power  rightly 
applied  could  sustain  over  200  pounds  in  the  air  at  a horizontal 
velocity  of  somewhat  over  60  feet  a second. 

As  this  statement  has  been  misconstrued,  let  me  point  out 
that  it  refers  to  surfaces,  used  without  guys,  or  other  adjuncts, 
which  would  create  friction ; that  the  horse-power  in  question 
is  that  actually  expended  in  the  thrust,  and  that  it  is  predicated 
only  on  a rigorously  horizontal  flight.  This  implies  a large 
deduction  from  the  power  in  the  actual  machine,  where  the 
brake  horse-power  of  the  engine,  after  a requisite  allowance  for 
loss  in  transmission  to  the  propellers,  and  for  their  slip  on  the 
air,  will  probably  be  reduced  to  from  one-half  to  one-quarter  of 
its  nominal  amount ; where  there  is  great  friction  from  the  en- 
forced use  of  guys  and  other  adjuncts  ; but  above  all  where  there 
is  no  way  to  insure  absolutely  horizonal  flight  in  free  air.  All 
these  things  allowed  for,  however,  since  it  seemed  to  me  possible 
to  provide  an  engine  which  should  give  a horse-power  for  some- 
thing like  10  pounds  of  weight,  there  was  still  enough  to  justify 
the  statement  that  we  possessed  in  the  steam-engine,  as  then 
constructed,  or  in  other  heat  engines,  more  than  the  indispen- 
sable power,  though  it  was  added  that  this  was  not  asserting 
that  a system  of  supporting  surfaces  could  be  securely  guided 
through  the  air  or  safely  brought  to  the  ground,  and  that  these 
and  like  considerations  were  of  quite  another  order,  and  be- 
longed to  some  inchoate  art  which  I might  provisionally  call 
aerodromics. 

These  important  conclusions  were  reached  before  the  actual 
publication  of  the  volume,  and  a little  later  others  on  the  nature 
of  the  movements  of  air,  which  were  published  under  the  title 
of  “ The  Internal  Work  of  the  Wind  ” (Smithsonian  Contribu- 


128 


THE  AERONAUTICAL  ANNUAL. 


tions  to  Knowledge,  Volume  XXVII.,  1893,  No.  884).  The 
latter  were  founded  on  experiments  independent  of  the  former, 
and  which  led  to  certain  theoretical  conclusions  unverified  in 
practice.  Among  the  most  striking  and  perhaps  paradoxical 
of  these,  was  that  a suitably  disposed  free  body  might  under 
certain  conditions  be  sustained  in  an  ordinary  wind,  and  even 
advance  against  it  without  the  expenditure  of  any  energy  from 
within. 

The  first  stage  of  the  investigation  was  now  over,  so  far  as 
that  I had  satisfied  myself  that  mechanical  flight  was  possible 
with  the  power  we  could  hope  to  command,  if  only  the  art  of 
directing  that  power  could  be  acquired. 

The  second  stage  (that  of  the  acquisition  of  this  art)  I now 
decided  to  take  up.  It  may  not  be  out  of  place  to  recall  that 
at  this  time,  only  six  years  ago,  a great  many  scientific  men 
treated  the  whole  subject  with  entire  indifference  as  unworthy  of 
attention  or  as  outside  of  legitimate  research,  the  proper  field 
for  the  charlatan,  and  one  on  which  it  was  scarcely  prudent  for 
a man  with  a reputation  to  lose,  to  enter. 

The  record  of  my  attempts  to  acquire  the  art  of  flight  may 
commence  with  the  year  1889,  when  I procured  a stuffed 
frigate  bird,  a California  condor,  and  an  albatross,  and  at- 
tempted to  move  them  upon  the  whirling  table  at  Allegheny. 
The  experiments  were  very  imperfect  and  the  records  are  un- 
fortunately lost,  but  the  important  conclusion  to  which  they 
led  was  that  a stuffed  bird  could  not  be  made  to  soar  except 
at  speeds  which  were  unquestionably  very  much  greater  than 
what  served  to  sustain  the  living  one,  and  the  earliest  experi- 
ments and  all  sul^sequent  ones  with  actually  flying  models 
have  shown  that  thus  far  we  cannot  carry  nearly  the  weights 
which  Nature  does  to  a given  sustaining  surface,  without  a 
power  much  greater  than  she  employs.  At  the  time  these  ex- 
periments were  begun,  Penaud’s  ingenious  but  toy-like  model 
was  the  only  thing  which  could  sustain  itself  in  the  air  for  even 
a few  seconds,  and  calculations  founded  upon  its  performance 
sustained  the  conclusion  that  the  amount  of  power  required  in 
actual  free  flight  was  far  greater  than  that  demanded  by  the 


EXPERIMENTS  IN  MECHANICAL  FLIGHT. 


129 


theoretical  enunciation.  In  order  to  learn  under  what  condi- 
tions the  aerodrome  should  be  balanced  for  horizontal  flight,  I 
constructed  over  30  modifications  of  the  rubber-driven  model, 
and  spent  many  months  in  endeavoring  from  these  to  ascertain 
the  laws  of  “ balancing  ” ; that  is,  of  stability  leading  to  horizontal 
flight.  Most  of  these  models  had  two  propellers,  and  it  was 
extremely  difficult  to  build  them  light  and  strong  enough. 
Some  of  them  had  superposed  wings ; some  of  them  curved  and 
some  plane  wings ; in  some  the  propellers  were  side  by  side, 
in  others  one  propeller  was  at  the  front  and  the  other  at  the 
rear,  and  so  every  variety  of  treatment  was  employed,  but  all 
were  at  first  too  heavy,  and  only  those  flew  successfully  which 
had  from  3 to  4 feet  of  sustaining  surface  to  a pound  of  weight, 
a proportion  which  is  far  greater  than  Nature  employs  in  the 
soaring  bird,  where  in  some  cases  less  than  half  a foot  of 
sustaining  surface  is  used  to  a pound.  It  had  been  shown  in 
the  “ Experiments  in  Aerodynamics  ” that  the  centre  of  press- 
ure on  an  inclined  plane  advancing  was  not  at  the  centre  of 
figure,  but  much  in  front  of  it,  and  this  knowledge  was  at  first 
nearly  all  I possessed  in  balancing  these  early  aerodromes. 
Even  in  the  beginning,  also,  I met  remarkable  difficulty  in 
throwing  them  into  the  air,  and  devised  numerous  forms  of 
launching  apparatus  which  were  all  failures,  and  it  was  neces- 
sary to  keep  the  construction  on  so  small  a scale  that  they 
could  be  cast  from  the  hand. 

The  earliest  actual  flights  with  these  were  extremely  irregular 
and  brief,  lasting  only  from  three  to  four  seconds.  They  were 
made  at  Allegheny  in  March,  1891,  but  these  and  all  subsequent 
ones  were  so  erratic  and  so  short  that  it  was  possible  to  learn 
very  little  from  them.  Penaud  states  that  he  once  obtained  a 
flight  of  13  seconds.  I never  got  as  much  as  this,  but  ordinarily 
little  more  than  half  as  much,  and  came  to  the  conclusion  that  in 
order  to  learn  the  art  of  mechanical  flight  it  was  necessary  to 
have  a model  which  would  keep  in  the  air  for  at  any  rate  a longer 
period  than  these,  and  move  more  steadily.  Rubber  twisted  in 
the  way  that  Penaud  used  it,  will  practically  give  about  300  foot- 
pounds to  a pound  of  weight,  and  at  least  as  much  must  be 


130 


THE  AERONAUTICAL  ANNUAL. 


allowed  for  the  weight  of  the  frame  on  which  the  rubber  is 
strained.  Twenty  pounds  of  rubber  and  frame,  then,  would  give 
3,000  foot-pounds,  or  one-horse  power  for  less  than  six  seconds. 
A steam-engine,  having  apparatus  for  condensing  its  steam, 
weighing  in  all  lo  pounds  and  carrying  lo  pounds  of  fuel,  would 
possess  in  this  fuel,  supposing  that  but  one-tenth  of  its  theoret- 
ical capacity  is  utilized,  many  thousand  times  the  power  of  an 
equal  weight  of  rubber,  or  at  least  one-horse  power  for  some 
hours.  Provided  the  steam  could  be  condensed  and  the  water 
re-used,  then,  the  advantage  of  the  steam  over  the  spring  motor 
was  enormous,  even  in  a model  constructed  only  for  the  purpose 
of  study.  But  the  construction  of  a steam-driven  aerodrome 
was  too  formidable  a task  to  be  undertaken  lightly,  and  I ex- 
amined the  capacities  of  condensed  air,  carbonic  acid  gas,  of 
various  applications  of  electricity,  whether  in  the  primary  or 
storage  battery,  of  hot-water  engines,  of  inertia  motors,  of  the 
gas  engine,  and  of  still  other  material.  The  gas  engine  promised 
best  of  all  in  theory,  but  it  was  not  yet  developed  in  a suitable 
form.  The  steam-engine,  as  being  an  apparently  familiar  con- 
struction, promised  best  in  practice,  but  in  taking  it  up,  I,  to 
my  cost,  learned  that  in  the  special  application  to  be  made  of  it, 
little  was  really  familiar  and  everything  had  to  be  learned  by 
experiment.  I had  myself  no  previous  knowledge  of  steam  en- 
gineering, nor  any  assistants  other  than  the  very  capable  work- 
men employed.  I well  remember  my  difficulties  over  the  first 
aerodrome  (No.  o),  when  everything,  not  only  the  engine,  but 
the  boilers  which  were  to  supply  it,  the  furnaces  which  were  to 
heat  it,  the  propellers  which  were  to  advance  it,  the  hull  which 
was  to  hold  all  these,  — were  all  things  to  be  originated,  in  a 
construction  which,  as  far  as  I knew,  had  never  yet  been  under- 
taken by  any  one. 

It  was  necessary  to  make  a beginning,  however,  and  a com- 
pound engine  was  planned  which,  when  completed,  weighed  about 
4 pounds,  and  which  could  develop  rather  over  a horse-power 
with  6o  pounds  of  steam,  which  it  was  expected  could  be  fur- 
nished by  a series  of  tubular  boilers  arranged  in  “bee-hive” 
form,  and  the  whole  was  to  be  contained  in  a hull  about  5 feet  in 


GROVER  C.  BERGOOLL 


EXPERIMENTS  IN  MECHANICAL  FLIGHT.  131 

length  and  10  inches  in  diameter.  This  hull  was,  as  in  the  con- 
struction of  a ship,  to  carry  all  adjuncts.  In  front  of  it  projected 
a steel  rod,  or  bowsprit,  about  its  own  length,  and  one  still 
longer  behind.  The  engines  rotated  two  propellers,  each  about 
30  inches  in  diameter,  which  were  on  the  end  of  long  shafts  dis- 
posed at  an  acute  angle  to  each  other  and  actuated  by  a single 
gear  driven  from  the  engine.  A single  pair  of  large  wings  con- 
tained about  50  square  feet,  and  a smaller  one  in  the  rear  about 
half  as  much,  or  in  all  some  75  feet,  of  sustaining  surface,  for  a 
weight  which  it  was  expected  would  not  exceed  25  pounds. 

Although  this  aerodrome  was  in  every  way  a disappointment, 
its  failure  taught  a great  many  useful  lessons.  It  had  been 
built  on  the  large  scale  described,  with  very  little  knowledge  of 
how  it  was  to  be  launched  into  the  air,  but  the  construction 
developed  the  fact  that  it  was  not  likely  to  be  launched  at  all, 
since  there  was  a constant  gain  in  weight  over  the  estimate  at 
each  step,  and  when  the  boilers  were  completed,  it  was  found 
that  they  gave  less  than  one-half  the  necessary  steam,  owing 
chiefly  to  the  inability  to  keep  up  a proper  fire.  The  wings 
yielded  so  as  to  be  entirely  deformed  under  a slight  press- 
ure of  the  air,  and  it  was  impossible  to  make  them  stronger 
without  making  them  heavier,  where  the  weight  was  already 
prohibitory.  The  engines  could  not  transmit  even  what  feeble 
power  they  furnished,  without  dangerous  tremor  in  the  long 
shafts,  and  there  were  other  difficulties.  When  the  whole  ap- 
proached completion,  it  was  found  to  weigh  nearer  50  pounds 
than  25,  to  develop  only  about  one-half  the  estimated  horse- 
power at  the  brake,  to  be  radically  weak  in  construction,  owing 
to  the  yielding  of  the  hull,  and  to  be,  in  short,  clearly  a hopeless 
case. 

The  first  steam-driven  aerodrome  had,  then,  proved  a failure, 
and  I reverted  during  the  remainder  of  the  year  to  simpler 
plans,  among  them  one  of  an  elementary  gasolene  engine. 

I may  mention  that  I was  favored  with  an  invitation  from 
Mr.  Maxim  to  see  his  great  flying-machine  at  Bexley,  in 
Kent,  where  I was  greatly  impressed  with  the  engineering  skill 
shown  in  its  construction,  but  I found  the  general  design  in- 


132 


THE  AERONAUTICAL  ANNUAL. 


compatible  with  the  conclusions  that  I had  reached  by  experi- 
ments with  small  models,  particularly  as  to  what  seemed  to  me 
advisable  in  the  carrying  of  the  centre  of  gravity  as  high  as 
was  possible  with  safety. 

In  1892  another  aerodrome  (No.  i),  which  was  to  be  used 
with  carbonic  acid  gas,  or  with  compressed  air,  was  commenced. 
The  weight  of  this  aerodrome  was  a little  over  4J  pounds,  and 
the  area  of  the  supporting  surfaces  6i  square  feet.  The  engines 
developed  but  a small  fraction  of  a horse-power,  and  they  were 
able  to  give  a dead  lift  of  only  about  one-tenth  of  the  weight 
of  the  aerodrome,  giving  relatively  less  power  to  weight  than 
that  obtained  in  the  large  aerodrome  already  condemned. 

Toward  the  close  of  this  year  was  taken  up  the  more  careful 
study  of  the  position  of  the  centre  of  gravity  with  reference  to 
the  line  of  thrust  from  the  propellers,  and  to  the  centre  of  press- 
ure. The  centre  of  gravity  was  carried  as  high  as  was  con- 
sistent with  safety,  the  propellers  being  placed  so  high,  with 
reference  to  the  supporting  wings,  that  the  intake  of  air  was 
partly  from  above  and  partly  from  below  these  latter.  The 
lifting  power  (i.e.,  the  dead-lift)  of  the  aerodromes  was  de- 
termined in  the  shop  by  a very  useful  contrivance  which  I have 
called  the  “ pendulum,”  which  consists  of  a large  pendulum 
which  rests  on  knife  edges,  but  is  prolonged  above  the  points 
of  support,  and  counterbalanced  so  as  to  present  a condition  of 
indifferent  equilibrium.  Near  the  lower  end  of  this  pendulum 
the  aerodrome  is  suspended,  and  when  power  is  applied  to  it, 
the  reaction  of  the  propellers  lifts  the  pendulum  through  a cer- 
tain angle.  If  the  line  of  thrust  passes  through  the  centre  of 
gravity,  it  will  be  seen  that  the  sine  of  this  angle  will  be  the 
fraction  of  the  weight  lifted,  and  thus  the  dead-lift  power  of  the 
engines  becomes  known.  Another  aerodrome  was  built,  but 
both,  however  constructed,  were  shown  by  this  pendulum  test 
to  have  insufficient  power,  and  the  year  closed  with  disap- 
pointment. 

Aerodrome  No.  3 was  of  stronger  and  better  construction,  and 
the  propellers,  which  before  this  had  been  mounted  on  shafts 
inclined  to  each  other  in  a V-like  form,  were  replaced  by  par- 


EXPERIMENTS  IN  MECHANICAL  FLIGHT. 


133 


allel  ones.  Boilers  of  the  Serpolet  type  (that  is,  composed  of 
tubes  of  nearly  capillary  section)  were  experimented  with  at 
great  cost  of  labor  and  no  results ; and  they  were  replaced  with 
coil  boilers.  For  these  I introduced,  in  April,  1893,  a modifi- 
cation of  the  selopile  blast,  which  enormously  increased  the 
heat-giving  power  of  the  fuel  (which  was  then  still  alcohol), 
and  with  this  blast  for  the  first  time  the  boilers  began  to  give 
steam  enough  for  the  engines.  It  had  been  very  difficult  to 
introduce  force  pumps  which  would  work  effectively  on  the 
small  scale  involved,  and  after  many  attempts  to  dispense  with 
their  use  by  other  devices,  the  acquisition  of  a sufficiently 
strong  pump  was  found  to  be  necessary  in  spite  of  its  weight, 
but  was  only  secured  after  long  experiment.  It  may  be  added 
that  all  the  aerodromes  from  the  very  nature  of  their  construction 
were  wasteful  of  heat,  the  industrial  efficiency  little  exceeding  half 
of  one  per  cent.,  or  from  one-tenth  to  one-twentieth  that  of  a sta- 
tionary engine  constructed  under  favorable  conditions.  This  last 
aerodrome  lifted  nearly  30  per  cent,  of  its  weight  upon  the  pen- 
dulum, which  implied  that  it  could  lift  much  more  than  its  weight 
when  running  on  a horizontal  track,  and  its  engines  were  capable 
of  running  its  50-centimetre  propellers  at  something  over  700 
turns  per  minute.  There  was,  however,  so  much  that  was  unsat- 
isfactory about  it,  that  it  was  deemed  best  to  proceed  to  another 
construction  before  an  actual  trial  was  made  in  the  field,  and  a 
new  aerodrome,  designated  as  No.  4,  was  begun.  This  last  was 
an  attempt,  guided  by  the  weary  experience  of  preceding  fail- 
ures, to  construct  one  whose  engines  should  run  at  a much 
higher  pressure  than  heretofore,  and  be  much  more  economical 
in  weight.  The  experiments  with  the  Serpolet  boilers  having 
been  discontinued,  the  boiler  was  made  with  a continuous  helix 
of  copper  tubing,  which  as  first  employed  was  about  three  milli- 
metres internal  diameter ; and  it  may  be  here  observed  that  a 
great  deal  of  time  was  subsequently  lost  in  attempts  to  construct 
a more  advantageous  form  of  boiler  for  the  actual  purposes  than 
this  simple  one,  which  with  a larger  coil  tube  eventually  proved 
to  be  the  best ; so  that  later  constructions  have  gone  back  to 
this  earlier  type.  A great  deal  of  time  was  lost  in  these  experi- 


13^ 


THE  AERONAUTICAL  ANNUAL. 


merits  from  my  own  unfamiliarity  with  steam  engineering,  but 
it  may  also  be  said  that  there  was  little  help  either  from  books 
or  from  counsel,  for  everything  was  here  sui  ge^ieris,  and  had  to 
be  worked  out  from  the  beginning.  In  the  construction  which 
had  been  reached  by  the  middle  of  the  third  year  of  experiment, 
and  which  has  not  been  greatly  differed  from  since,  the  boiler 
was  composed  of  a coil  of  copper  in  the  shape  of  a hollow  helix, 
through  the  centre  of  which  the  blast  from  the  aelopile  was 
driven,  the  steam  and  water  passing  into  a vessel  I called  the 
“ separator,”  whence  the  steam  was  led  into  the  engines  at  a 
pressure  of  from  70  to  100  pounds  (a  pressure  which  has  since 
been  considerably  exceeded). 

From  the  very  commencement  of  this  long  investigation  the 
great  difficulty  was  in  keeping  down  the  weight,  for  any  of  the 
aerodromes  could  probably  have  flown  had  they  been  built  light 
enough,  and  in  every  case  before  the  construction  was  com- 
pleted the  weight  had  so  increased  beyond  the  estimate,  that 
the  aerodrome  was  too  heavy  to  fly,  and  nothing  but  the  most 
persistent  resolution  kept  me  in  continuing  attempts  to  reduce 
it  after  further  reduction  seemed  impossible.  Toward  the  close 
of  the  year  ( 1 893  ) I had,  however,  finally  obtained  an  aerodrome 
with  mechanical  power,  as  it  seemed  to  me,  to  fly,  and  I pro- 
cured, after  much  thought  as  to  where  this  flight  should  take 
place,  a small  house-boat,  to  be  moored  somewhere  in  the 
Potomac  ; but  the  vicinity  of  Washington  was  out  of  the  question, 
and  no  desirable  place  was  found  nearer  than  thirty  miles  below 
the  city.  It  was  because  it  was  known  that  the  aerodrome  might 
have  to  be  set  off  in  the  face  of  a wind,  which  might  blow  in 
any  direction,  and  because  it  evidently  was  at  first  desirable 
that  it  should  light  in  the  water  rather  than  on  the  land, 
that  the  house-boat  was  selected  as  the  place  for  the  launch. 
The  aerodrome  (No.  4)  weighed  between  9 and  10  pounds,  and 
lifted  40  per  cent,  of  this  on  the  pendulum  with  60  pounds  of 
steam  pressure,  a much  more  considerable  amount  than  was 
theoretically  necessary  for  horizontal  flight.  And  now  the  con- 
struction of  a launching  apparatus,  dismissed  for  some  years, 
was  resumed.  Nearly  every  form  seemed  to  have  been  experi- 


EXPERIMENTS  IN  MECHANICAL  FLIGHT. 


135 


mented  with  unsuccessfully  in  the  smaller  aerodromes.  Most  of 
the  difficulties  were  connected  with  the  fact  that  it  is  necessary 
for  an  aerodrome,  as  it  is  for  a soaring  bird,  to  have  a certain 
considerable  initial  velocity  before  it  can  advantageously  use 
its  own  mechanism  for  flight,  and  the  difficulties  of  imparting 
this  initial  velocity  with  safety  are  surprisingly  great,  and  in  the 
open  air  are  beyond  all  anticipation. 

Here,  then,  commences  another  long  story  of  delay  and  dis- 
appointment in  these  efforts  to  obtain  a successful  launch.  To 
convey  to  the  reader  an  idea  of  its  difficulties,  a few  extracts 
from  the  diary  of  the  period  are  given.  (It  will  be  remembered 
that  each  attempt  involved  a journey  of  thirty  miles  each  way.) 

Nov.  18,  1893.  Having  gone  down  to  the  house-boat, 
preparatory  to  the  first  launch,  in  which  the  aerodrome  was  to  be 
cast  from  a springing  piece  beneath,  it  was  found  impossible 
to  hold  it  in  place  on  this  before  launching,  without  its  being 
prematurely  torn  from  its  support,  although  there  was  no  wind 
except  a moderate  breeze ; and  the  party  returned  after  a day’s 
fruitless  effort. 

Two  days  later  a relative  calm  occurred  in  the  afternoon  of  a 
second  visit,  when  the  aerodrome  was  mounted  again,  but, 
though  the  wind  was  almost  imperceptible,  it  was  sufficient 
to  wrench  it  about  so  that  at  first  nothing  could  be  done, 
and  when  steam  was  gotten  up,  the  burning  alcohol  blew  about 
so  as  to  seriously  injure  the  inflammable  parts.  Finally,  the 
engines  being  under  full  steam,  the  launch  was  attempted, 
but,  owing  to  the  difficulties  alluded  to  and  to  a failure  in  the 
construction  of  the  launching  piece,  the  aerodrome  was  thrown 
down  upon  the  boat,  fortunately  with  little  damage. 

Whatever  form  of  launch  was  used  it  became  evident  at  this 
time  that  the  aerodrome  must  at  any  rate  be  firmly  held,  up  to 
the  very  instant  of  release,  and  a device  was  arranged  for  clamp- 
ing it  to  the  launching  apparatus. 

On  November  24th  another  attempt  was  made  to  launch, 
which  was  rendered  impossible  by  a very  moderate  wind  indeed. 

On  November  27th  a new  apparatus  was  arranged  to  merely 
drop  the  aerodrome  over  the  water,  with  the  hope  that  it  would 


THE  AERONAUTICAL  ANNUAL. 


136 

get  up  sufficient  speed  before  reaching  the  surface  to  soar,  but 
it  was  found  that  a very  gentle  intermittent  breeze  (probably 
not  more  than  three  or  four  miles  an  hour)  was  sufficient  to 
make  it  impossible  even  to  prepare  to  drop  the  aerodrome 
toward  the  water  with  safety. 

It  is  difficult  to  give  an  idea  in  few  words  of  the  nature  of 
the  trouble,  but  unless  one  stands  v.^ith  the  machine  in  the 
open  air  he  can  form  no  conception  of  what  the  difficulties 
are  which  are  peculiar  to  practice  in  the  open,  and  which 
do  not  present  themselves  to  the  constructor  in  the  shop, 
nor  probably  to  the  mind  of  the  reader. 

December  ist,  another  failure;  December  7th,  another; 
December  1 1 th,  another ; December  20th,  another;  December 
2 1st,  another.  These  do  not  all  involve  a separate  journey,  but 
five  separate  trips  were  made  of  a round  distance  of  60  miles 
each  before  the  close  of  the  season.  It  may  be  remembered 
that  these  attempts  were  in  a site  far  from  the  conveniences  of 
the  workshop,  and  under  circumstances  which  took  up  a great 
deal  of  time,  for  some  hours  were  spent  on  mounting  the  aero- 
drome on  each  occasion,  and  the  year  closed  without  a single  cast 
of  it  into  the  air.  It  was  not  known  how  it  would  have  behaved 
there,  for  there  had  not  been  a launch,  even,  in  nine  trials,  each 
one  representing  an  amount  of  trouble  and  difficulty  which  this 
narrative  gives  no  adequate  idea  of. 

I pass  over  a long  period  of  subsequent  baffled  effort,  with 
the  statement  that  numerous  devices  for  launching  were  tried  in 
vain,  and  that  nearly  a year  passed  before  one  was  effected. 

Six  trips  and  trials  were  made  in  the  first  six  months  of  1894, 
without  securing  a launch.  On  the  24th  of  October  a new 
launching  piece  was  tried  for  the  first  time,  which  embodied 
all  the  requisites  whose  necessity  was  taught  by  previous 
experience,  and,  saving  occasional  accidents,  the  launching  was 
from  this  time  forward  accomplished  with  comparatively  little 
difficulty. 

The  aerodromes  were  now  for  the  first  time  put  fairly  in  the 
air,  and  a new  class  of  difficulties  arose,  due  to  a cause  which 
was  at  first  obscure,  — for  two  successive  launches  of  the  same 


EXPERIMENTS  IN  MECHANICAL  FLIGHT, 


137 


aerodrome,  under  conditions  as  near  alike  as  possible,  would  be 
followed  by  entirely  different  results.  For  example,  in  the  first 
case  it  might  be  found  rushing,  not  falling,  forward  and  down- 
ward into  the  water  under  the  impulse  of  its  own  engines; 
in  the  second  case,  with  every  condition  from  observation  ap- 
parently the  same,  it  might  be  found  soaring  upward  until  its 
wings  made  an  angle  of  60  degrees  with  the  horizon,  and, 
unable  to  sustain  itself  at  such  a slope,  sliding  backward  into 
the  water. 

After  much  embarrassment  the  trouble  was  discovered  to  be 
due  to  the  fact  that  the  wings,  though  originally  set  at  precisely 
the  same  position  and  same  angle  in  the  two  cases,  were  irregu- 
larly deflected  by  the  upward  pressure  of  the  air,  so  that  they 
no  longer  had  the  form  which  they  appeared  to  possess  but  a 
moment  before  they  were  upborne  by  it,  and  so  that  a very 
minute  difference,  too  small  to  be  certainly  noted,  exaggerated 
by  this  pressure,  might  cause  the  wind  of  advance  to  strike 
either  below  or  above  the  wing  and  to  produce  the  salient  differ- 
ence alluded  to.  When  this  was  noticed  all  aerodromes  were 
inverted,  and  sand  was  dredged  uniformly  over  the  wings  until 
its  weight  represented  that  of  the  machine.  The  flexure  of 
the  wings  under  these  circumstances  must  be  nearly  that  in  free 
air,  and  it  was  found  to  distort  them  beyond  all  anticipation. 
Here  commences  another  series  of  trials  in  which  the  wings  were 
strengthened  in  various  ways,  but  in  none  of  which,  without  in- 
curring a prohibitive  weight,  was  it  possible  to  make  them 
strong  enough.  Various  methods  of  guying  them  were  tried, 
and  they  were  rebuilt  on  different  designs,  — a slow  and  expen- 
sive process.  Finally,  it  may  be  said,  in  anticipation  (and 
largely  through  the  skill  of  Mr.  Reed,  the  foreman  of  the  work), 
the  wings  were  rendered  strong  enough  without  excessive  weight, 
but  a year  or  more  passed  in  these  and  other  experiments. 

In  the  latter  part  of  1894  two  steel  aerodromes  had  already 
been  built  which  sustained  from  40  to  50  per  cent,  of  their 
dead-lift  weight  on  the  pendulum,  and  each  of  which  was  ap- 
parently supplied  with  much  more  than  sufficient  power  for 
horizontal  flight  (the  engine  and  all  the  moving  parts  furnish- 


138 


THE  AERONAUTICAL  ANNUAL. 


ing  over  one-horse  power  at  the  brake  weighed  in  one  of  these 
but  26  ounces)  ; but  it  may  be  remarked  that  the  boilers 
and  engines  in  lifting  this  per  cent,  of  the  weight  did  so  only 
at  the  best  performance  in  the  shop,  and  that  nothing  like  this 
could  be  counted  upon  for  regular  performance  in  the  open. 
Every  experiment  with  the  launch,  when  the  aerodrome  de- 
scended into  the  water,  not  gently,  but  impelled  by  the  mis- 
directed power  of  its  own  engines,  resulted  at  this  stage  in  severe 
strains  and  local  injury,  so  that  repairing,  which  was  almost  re- 
building, constantly  went  on, — a hard  but  necessary  condition 
attendant  on  the  necessity  of  trial  in  the  free  air.  It  was  gradu- 
ally found  that  it  was  indispensable  to  make  the  frame  stronger 
than  had  hitherto  been  done,  though  the  absolute  limit  of 
strength  consistent  with  weight  seemed  to  have  been  already 
reached,  and  the  year  1895  was  chiefly  devoted  to  the  labor  on 
the  wings  and  what  seemed  at  first  the  hopeless  task  of  improv- 
ing the  construction  so  that  it  might  be  stronger  without  addi- 
tional weight,  when  every  gramme  of  weight  had  already  been 
scrupulously  economized.  With  this  went  on  attempts  to  carry 
the  effective  power  of  the  burners,  boilers,  and  engines  further, 
and  modification  of  the  internal  arrangement  and  a general  dis- 
position of  the  parts  such  that  the  wings  could  be  placed  further 
forward  or  backward  at  pleasure,  to  more  readily  meet  the  con- 
ditions necessary  for  bringing  the  centre  of  gravity  under  the 
centre  of  pressure.  So  little  had  even  now  been  learned  about 
the  system  of  balancing  in  the  open  air  that  at  this  late  day 
recourse  was  again  had  to  rubber  models,  of  a different  char- 
acter, however,  from  those  previously  used,  for  in  the  latter  the 
rubber  was  strained,  not  twisted.  These  experiments  took 
up  an  inordinate  time,  though  the  flight  obtained  from  the 
models  thus  made  was  somewhat  longer  and  much  steadier 
than  that  obtained  with  the  Penaud  form,  and  from  them  a 
good  deal  of  valuable  information  was  gained  as  to  the  number 
and  position  of  the  wings,  and  as  to  the  effectiveness  of  differ- 
ent forms  and  dispositions  of  them.  By  the  middle  of  the  year 
a launch  took  place  with  a brief  flight,  where  the  aerodrome 
shot  down  into  the  water  after  a little  over  50  yards.  It  was 


EXPERIMENTS  IN  MECHANICAL  FLIGHT. 


139 


immediately  followed  by  one  in  which  the  same  aerodrome  rose 
at  a considerable  incline  and  fell  backward,  with  scarcely  any 
advance  after  sustaining  itself  rather  less  than  ten  seconds, 
and  these  and  subsequent  attempts  showed  that  the  problem  of 
disposing  of  the  wings  so  that  they  would  not  yield,  and  of  ob- 
taining a proper  “ balance,”  was  not  yet  solved. 

Briefly  it  may  be  said  that  the  year  1895  gave  small  results 
for  the  labor  with  which  it  was  filled,  and  that  at  its  close  the 
outlook  for  further  substantial  improvement  seemed  to  be 
almost  hopeless,  but  it  was  at  this  time  that  final  success  was 
drawing  near.  Shortly  after  its  close  I became  convinced  that 
substantial  rigidity  had  been  secured  for  the  wings ; that  the 
frame  had  been  made  stronger  without  prohibitive  weight,  and 
that  a degree  of  accuracy  in  the  balance  had  been  obtained 
which  had  not  been  hoped  for.  Still  there  had  been  such  a 
long  succession  of  disasters  and  accidents  in  the  launching  that 
hope  was  low  when  success  finally  came. 

I have  not  spoken  here  of  the  aid  which  I received  from 
others,  and  particularly  from  Doctor  Carl  Barus  and  Mr.  J.  E. 
Watkins,  who  have  been  at  different  times  associated  with  me 
in  the  work.  Mr.  R.  L.  Reed’s  mechanical  skill  has  helped  me 
everywhere,  and  the  lightness  and  efficiency  of  the  engines  are 
in  a large  part  due  to  Mr.  L.  C.  Maltby. 


[From  Aero.  Ann.,  1897.] 


THE  AERODROMES  IN  FLIGHT. 


The  successful  flights  of  Dr.  Langley’s  aerodrome  were  wit- 
nessed by  Dr.  Bell  and  described  by  him  as  follows : ^ 

Through  the  courtesy  of  Dr.  S.  P.  Langley,  Secretary  of  the 
Smithsonian  Institution,  I have  had,  on  various  occasions,  the 
privilege  of  witnessing  his  experiments  with  aerodromes,  and 
especially  the  remarkable  success  attained  by  him  in  experi- 
ments made  upon  the  Potomac  river  on  Wednesday,  May  6, 
1896,  which  led  me  to  urge  him  to  make  public  some  of  these 
results. 

I had  the  pleasure  of  witnessing  the  successful  flight  of  some 
of  these  aerodromes  more  than  a year  ago,  but  Dr.  Langley’s 
reluctance  to  make  the  results  public  at  that  time  prevented  me 
from  asking  him,  as  I have  done  since,  to  let  me  give  an 
account  of  what  I saw. 

On  the  date  named  two  ascensions  were  made  by  the  aero- 
drome, or  so-called  “flying-machine,”  which  I will  not  describe 
here  further  than  to  say  that  it  appeared  to  me  to  be  built 
almost  entirely  of  metal,  and  driven  by  a steam-engine  which  I 
have  understood  was  carrying  fuel  and  a water  supply  for  a very 
brief  period,  and  which  was  of  extraordinary  lightness. 

The  absolute  weight  of  the  aerodrome,  including  that  of  the 
engine  and  all  appurtenances,  was,  as  I was  told,  about  25 
pounds,  and  the  distance  from  tip  to  tip  of  the  supporting  sur- 
faces was,  as  I observed,  about  12  or  14  feet.  The  method  of 
propulsion  was  by  aerial  screw-propellers,  and  there  was  no 
gas  or  other  aid  for  lifting  it  in  the  air  except  its  own  internal 
energy. 

On  the  occasion  referred  to,  the  aerodrome,  at  a given  signal, 
started  from  a platform  about  20  feet  above  the  water,  and  rose 
at  first  directly  in  the  face  of  the  wind,  moving  at  all  times  with 
remarkable  steadiness,  and  subsequently  swinging  around  in 
large  curves  of,  perhaps,  a hundred  yards  in  diameter,  and  con- 
tinually ascending  until  its  steam  was  exhausted,  when,  at  a 
lapse  of  about  a minute  and  a half,  and  at  a height  which  I 


* “ Nature,”  London,  May  28,  1896. 
(140) 


THE  AERODROMES  IN  FLIGHT. 


I41 

judged  to  be  between  80  and  100  feet  in  the  air,  the  wheels 
ceased  turning,  and  the  machine,  deprived  of  the  aid  of  its  pro- 
pellers, to  my  surprise  did  not  fall,  but  settled  down  so  softly 
and  gently  that  it  touched  the  water  without  the  least  shock, 
and  was  in  fact  immediately  ready  for  another  trial. 

In  the  second  trial,  which  followed  directly,  it  repeated  in 
nearly  every  respect  the  actions  of  the  first,  except  that  the 
direction  of  its  course  was  different.  It  ascended  again  in  the 
face  of  the  wind,  afterwards  moving  steadily  and  continually  in 
large  curves  accompanied  with  a rising  motion  and  a lateral  ad- 
vance. Its  motion  was,  in  fact,  so  steady,  that  I think  a glass  of 
water  on  its  surface  would  have  remained  unspilled.  When  the 
steam  gave  out  again,  it  repeated  for  a second  time  the  experi- 
ence of  the  first  trial  when  the  steam  had  ceased,  and  settled 
gently  and  easily  down.  What  height  it  reached  at  this  trial  I 
cannot  say,  as  I was  not  so  favorably  placed  as  in  the  first ; but  I 
had  occasion  to  notice  that  this  time  its  course  took  it  over  a 
wooded  promontory,  and  I was  relieved  of  some  apprehension  in 
seeing  that  it  was  already  so  high  as  to  pass  the  tree-tops  by 
20  or  30  feet.  It  reached  the  water  i minute  and  31  sec- 
onds from  the  time  it  started,  at  a measured  distance  of  over 
900  feet  from  the  point  at  which  it  rose. 

This,  however,  was  by  no  means  the  length  of  its  flight.  I 
estimated  from  the  diameter  of  the  curve  described,  from  the 
number  of  turns  of  the  propellers  as  given  by  the  automatic 
counter,  after  due  allowance  for  slip,  and  from  other  measures, 
that  the  actual  length  of  flight  on  each  occasion  was  slightly 
over  3,000  feet.  It  is  at  least  safe  to  say  that  each  exceeded  half 
an  English  mile. 

From  the  time  and  distance  it  will  be  noticed  that  the 
velocity  was  between  20  and  25  miles  an  hour,  in  a course 
which  was  taking  it  constantly  “ up  hill.”  I may  add  that  pn  a 
previous  occasion  I have  seen  a far  higher  velocity  attained  by 
the  same  aerodrome  when  its  course  was  horizontal. 

I have  no  desire  to  enter  into  detail  further  than  I have 
done,  but  I cannot  but  add  that  it  seems  to  me  that  no  one  who 
was  present  on  this  interesting  occasion  could  have  failed  to 
recognize  that  the  practicability  of  mechanical  flight  had  been 
demonstrated. 

Alexander  Graham  Bell. 

Not  long  after  the  May  experiments  Dr.  Langley  went  abroad 
for  needed  rest  and  recreation,  and  in  the  autumn,  after  his 


142 


THE  AERONAUTICAL  ANNUAL. 


return,  further  experiments  were  tried.  On  the  28th  of  Novem- 
ber a flight  was  made  which  was  more  than  three-quarters  of  a 
mile  in  length,  the  time  occupied  being  precisely  one  minute 
and  three-quarters.  Mr.  Frank  G.  Carpenter  was  a fortunate 
witness  of  this,  the  longest  flight  ever  made,  and  with  Dr.  Lang- 
ley’s approval  he  wrote  a detailed  account  of  it  for  the  “ Wash- 
ington Star”  of  Dec.  12,  1896.  His  article  is  interesting  from 
beginning  to  end. 


1910.  Note. — The  active  interest  in  the  designing  and  flying  of  model  machines 
is  fortunately  increasing  steadily.  The  time  is  probably  far  distant  when  experi- 
ments with  models  will  cease  to  be  instructive. 

Those  who  have  made  considerable  advance  in  the  designing  of  models  may  find 
it  to  their  advantage  to  construct  their  models  upon  a scale  of  one-half  or  one-quarter 
that  of  a one-man  machine.  This  will  facilitate  computations.  Especial  attention 
is  called  to  the  subject  of  elasticity  in  the  rear  edges  of  sustaining  surfaces.  — Ed. 


[From  Aero.  Ann.,  1897.] 


THE  SCIENTIFIC  VALUE  OF  FLYING  MODELS. 


By  the  Editor. 


The  ultimate  object  of  aeronautical  study  and  experiment  is, 
of  course,  to  hasten  the  time  when  it  shall  be  possible  to  con- 
struct a practical  flying  machine. 

There  are  some  experimenters  who  think  that  the  day  of  the 
great  achievement  will  come  sooner  if  in  the  immediate  future 
we  give  the  most  of  our  time  and  thought  to  the  development 
of  the  motorless  air-sailer.  Others  think  that  more  rapid 
progress  will  be  made  through  the  development  of  the  self- 
propelled  aerodrome. 

It  is  quite  needless  to  attempt  at  this  time  to  say  who  is 
right;  time  will  show  us  all  that.  Moreover,  as  stated  in  the 
introductory  note,  whichever  branch  of  work  is  seriously  under- 
taken by  an  individual,  he  may  be  sure  that  while  working' 
upon  his  own  specialty  he  is  helping  those  engaged  in  the 
others  toward  their  common  goal. 

The  supreme  importance  which  attaches  to  the  flying  model 
comes  from  the  fact  that  experiments  with  it  may  be  made  to 
lessen  the  number  of  risks  of  human  life  and  limb.  We  have 
now  reached  the  stage  of  experiment  where  it  is  necessary  to 
use  all  possible  persuasion  to  keep  reasonably  near  terra  firma 
those  persons  who  have  nothing  but  the  courage  of  ignorance 

(143) 


144 


THE  AERONAUTICAL  ANNUAL. 


to  equip  them  for  ventures  in  the  air.  A part  of  the  glory  of 
the  work  of  ’96  at  Camp  Chanute  comes  from  the  fact  that  no 
one  of  the  experimenters  was  injured,  all  being  under  the  con- 
trol of  an  accomplished  scientist,  firm  and  clear-headed.  If  the 
lamented  Lilienthal,  with  his  great  knowledge  of  engineering, 
his  long  experience,  and  his  superb  self-control,  could  come  to 
his  untimely  end,  is  Fate  likely  to  be  kind  to  the  novice? 

Remembering  that  Lilienthal  said,  “ It  is  not  every  man’s 
business  to  launch  himself  into  space,”  and  knowing  that  there 
are  some  men  who  are  so  situated  that  experiments  with  models 
are  the  only  ones  which  they  can  undertake,  let  us  consider  the 
possible  value  of  the  results  of  such  experiments. 

We  can  readily  see  that  many  models  otherwise  excellent 
will  have  limitations  to  their  usefulness  because  of  the  laws 
governing  the  strength  of  materials.  In  designing  a model  it  is 
advisable  to  keep  in  mind,  so  far  as  possible,  the  probability  of 
the  retention  of  its  good  qualities  in  case  its  enlarged  counter- 
part is  constructed.  We  know  that  the  elements  of  strength 
contained  in  the  model,  which  will  also  appear  in  a full-sized 
machine,  are  those  which  have  come  from  the  engineering  skill 
shown  in  the  structure,  and  that  these  elements  must  be  so  far 
in  excess  of  the  actual  needs  of  the  model  that  they  will  offset 
the  great  loss  in  the  proportional  strength  of  materials  which 
occurs  when  the  size  of  machines  is  increased. 

I once  knew  of  an  imposing  piece  of  experimental  apparatus, 
having  several  hundred  square  feet  of  surface,  which  was  with- 
ered by  the  wind  because  the  designer  had  forgotten  the  simple 
point  just  mentioned. 

It  is  not  necessary  to  immediately  settle  the  question  as  to 
how  far  the  performance  of  a model  is  a demonstration  of  what 
can  be  done  with  its  enlarged  counterpart ; it  is  enough  for  the 
present  to  know  that  experiments  with  models  can  throw  much 
light  upon  several  subjects  that  are  now  imperfectly  understood. 
The  following  are  some  of  these : 

1.  Automatic  devices  for  preserving  equilibrium. 

2.  Disposition  of  surfaces. 

3.  Placing  of  screws. 


EDITORIAL. 


145 


4.  Curves  of  surfaces. 

5.  Relation  of  weight  to  area. 

6.  Relation  of  power  to  weight. 

7.  Effects  of  elasticity  in  sustaining  surfaces. 

Any  one  of  these  subjects  is  enough  to  occupy  an  experi- 
menter for  a long  time. 

In  regard  to  the  first  subject  it  will  be  noticed  that  the  con- 
tributors to  The  Annual  have  given  no  detailed  descriptions 
of  the  automatic  devices  which  they  have  tried.  This  is  because 
of  the  conservatism  which  leads  every  rational  experimenter  to 
withhold  details  from  the  public  until  his  own  tests  have  satisfied 
him  that  the  proper  time  has  come  to  make  an  announcement. 

Mr.  Chanute  in  his  book^  describes  many  attempts  which  have 
been  made  to  secure  automatic  equilibrium,  and  it  goes  with- 
out saying  that  no  one  will  begin  any  kind  of  aeronautical 
experiment  until  he  has  given  to  that  book  the  most  thorough 
study.  It  may  here  be  said  that  rolling  balls,  shifting  mercury 
ballast,  and  pendulum  devices  to  move  rudders  have  been  tried, 
but  none  of  these  have  so  far  given  satisfactory  results. 

If  there  is  one  man  whose  name  is  mentioned  oftener  than 
that  of  any  other  in  connection  with  the  subject  of  automatic 
equilibrium  it  is  that  of  Alphonse  Penaud,^  whose  flying  models 
attracted  much  attention  twenty  years  ago  and  recently  have 
attracted  still  more. 

In  1874  Mr.  T.  J.  Bennett,  of  Oxford,  brought  Penaud’s 
automatic  rudder  to  the  notice  of  the  Aeronautical  Society 
of  Great  Britain,  in  the  following  words : 

But  all  the  above  models  flew  by  accident,  there  being  no  special  means 
provided  for  maintaining  the  equilibrium  fore  and  aft.  This  problem  M. 
P6naud  has  solved  by  means  of  his  automatic  rudder. 

At  last  the  idea  occurred  to  him  of  placing  a small  horizontal  rudder 
behind  the  sustaining  planes,  and  inclined  at  a small  angle  to  them.  It 
succeeded  perfectly.  Its  mode  of  action  is  as  follows : 

The  centre  of  gravity  of  the  machine  is  placed  a little  in  front  of  the  centre 
of  pressure  of  the  aeroplane,  so  that  it  tends  to  make  the  model  descend  an 


Progress  in  Flying  Machines.”  Published  by  M.  N.  Forney,  N.Y.,  1894. 

2 A Frenchman,  now  of  honored  memory,  who  died  in  sorrow  and  disappointment 
in  1880,  before  reaching  the  age  of  thirty  years.  See  " Progress  in  Flying  Machines,”  pp. 
117-122. 


146 


THE  AERONAUTICAL  ANNUAL. 


incline ; but  in  so  doing  it  lessens  the  angle  of  inclination  of  the  aeroplane, 
and  the  speed  is  increased.  At  the  same  time  the  angle  of  the  horizontal 
rudder  is  increased,  and  the  pressure  of  air  on  its  upper  surface  causes  it  to 
descend ; but  as  the  machine  tends  to  turn  round  its  centre  of  gravity,  the 
front  part  is  raised  and  brought  back  to  the  horizontal  position.  If  owing 
to  the  momentum  gained  during  the  descent  the  machine  still  tends  upwards, 
the  angle  of  the  plane  is  increased  and  the  speed  decreased.  The  angle  of 
the  rudder  from  the  horizontal  being  reduced,  it  no  longer  receives  the 
pressure  of  the  air  on  its  superior  surface,  the  weight  in  front  reasserts  its 
power,  and  the  machine  descends.  Thus  by  the  alternate  action  of  the 
weight  in  front  and  the  rudder  behind  the  plane,  the  equilibrium  is 
maintained.  The  machine  during  flight,  owing  to  the  above  causes, 
describes  a series  of  ascents  and  descents,  after  the  manner  of  a sparrow. ‘ 


<70,  elastic  aeroplane ; automatic  rudder;  aerial  screw  centred  at  f;  frame  sup- 
porting aeroplane,  rudder,  and  screw;  India-rubber  in  a state  of  torsion,  attached  to  hook 
or  crank  at  f.  By  holding  the  aeroplane  {aa)  and  turning  the  screw  (cc)  the  necessary 
power  is  obtained  by  torsion.  — M.  Penaud^  1872. 


There  was  one  very  important  element  contained  in  the 
Penaud  model  shown  in  accompanying  cut,  and  that  was  the 
elasticity  of  the  stistaining  surfaces,  which  probably  had  much 
to  do  with  the  success  of  its  flights.  Even  at  the  risk  of  some 
repetition,  another  paragraph  is  here  quoted : 

As  rigid  aeroplanes  and  screws  were  employed  in  the  construction  of 
these  models  (previously  described)  they  flew  in  a hap-hazard  sort  of  a way. 

>It  will  occur  to  the  reader  that  the  flight  of  a sparrow  is  not  conspicuous  for  its  hori- 
zontality.  Any  one  who  experiments  with  motorless  gliders  (see  Aeronautical  Annu.vl, 
No.  I,  p.  166)  made  on  the  Penaud  principle  will  find  the  first  flights  decidedly  sparrow-like, 
but  he  will  also  find  that  by  varying  the  amount  of  weight  carried,  the  position  of  the  centre 
of  gravity,  and  the  size  and  angle  of  the  rudder,  the  undulation  of  the  flights  can  be  made 
less  and  less.  — Ed. 

2 See  Encyclopaedia  Britannica,  9th  edition,  N.Y.,  1879,  Vol.  IX.,  p.  321.  The  italics 
used  in  the  quotation  are  in  the  original. 


Grover  c.  bergdoll 


EDITORIAL.  147 

it  being  found  exceedingly  difficult  to  confer  on  them  the  necessary  degree 
of  stability  fore  and  aft  and  laterally.  M.  P6naud  succeeded  in  overcoming 
the  difficulty  in  question  by  the  invention  of  what  he  designates  his 
automatic  rudder.  This  consists  of  a small  elastic  aeroplane  placed  aft  or 
behind  the  principal  aeroplane,  which  is  also  elastic.  The  two  elastic 
aeroplanes  extend  horizontally  and  make  a slight  upward  angle  with  the 
horizon,  the  angle  made  by  the  smaller  aeroplane  (the  rudder)  being 
slightly  in  excess  of  that  made  by  the  larger. 

As  there  are  several  more  subjects  to  be  considered  in  this 
editorial,  more  space  must  not  be  given  to  this  matter  of  auto- 
matic stability.  To  say  that  experiments  with  models  can 
instruct  us  concerning  it,  is  almost  like  stating  an  axiom. 

We  come  now  to  the  second  subject:  the  disposition  of  sur- 
faces. The  nature  of  the  questions  which  arise  in  this  connec- 
tion can  best  be  explained  by  referring  the  reader  to  the 
previous  pages  where  Mr.  Chanute  has  described  the  permu- 
tations of  his  surfaces. 

Very  much  of  what  is  now  known  concerning  the  disposition 
of  surfaces  has  been  learned  from  the  flights  of  models.  I think 
that  no  experimenter  will  doubt  that  there  is  still  more  to  be 
learned. 

When  we  consider  the  third  subject,  the  placing  of  screws, 
we  shall  see  how  models  may  instruct  us  in  such  a manner  that 
undue  risks  of  life  and  limb  may  be  greatly  lessened.  The 
motorless  gliding  model  is  acted  upon  by  two  forces  — gravity 
and  the  pressure  of  the  air  upon  its  surfaces.  When  a motor 
and  propellers  are  used  there  is  a third  force,  the  thrust  of  the 
screws,  which  has  to  be  considered  in  all  calculations.  We  are 
justified  in  assuming  that  any  self-propelled  flying  machine 
must  have  the  excellence  of  equilibrium  of  the  best  gliding  ma- 
chine when  at  any  time  its  engines  are  stopped ; therefore  it  is 
possible  to  gain  knowledge  as  to  the  best  way  of  placing  the 
motor,  by  using,  in  place  of  the  motor,  ballast  having  the  weight 
and  general  form  of  the  motor  which  is  later  to  be  used. 

Where  the  line  of  screw-thrust  is  to  come,  so  that,  when  this 
third  force  is  applied,  the  equilibrium  of  the  machine  will  not  be 


148 


THE  AERONAUTICAL  ANNUAL. 


seriously  compromised,  is  a matter  upon  which  engineers  are 
not  fully  agreed,  and  therefore  an  amateur  may  well  refrain  from 
expressing  an  opinion.  The  difficulty  comes  in  the  travel  of  the 
centre  of  air  pressure,  which  is  now  imperfectly  understood. 

This  much  seems  probable,  that  if  engineers  will  furnish  work- 
ing hypotheses,  careful  laymen  may  test  these  in  placing  the 
screws  on  their  models,  and  in  that  way  do  useful  work. 

The  air-sailer  who  in  flight  first  adds  the  thrust  of  a screw  to 
the  forces  he  is  accustomed  to  deal  with  will  stand  in  need  of 
all  the  knowledge  which  can  be  gained  from  self-propelled 
models. 

The  fourth  subject  is,  the  curves  of  surfaces.  Lilienthal’s 
article  entitled  “ The  Best  Shapes  for  Wings,”  which  is  given  on 
previous  pages,  leaves  at  present  little  to  say  under  this  head. 

The  fifth  and  sixth  subjects  may  be  considered  together. 

The  relation  of  the  whole  weight  of  a model  to  the  area  of  its 
sustaining  surfaces  and  the  relation  of  the  power  used  to  the 
whole  weight  sustained  are  very  important  matters,  and  it  may 
be  assumed  that  when  model-flying  becomes  common,  many 
models  will  be  made  with  removable  motors,  so  that  with  one 
motor  comparative  tests  of  different  forms  of  models  can  be 
made,  and  useful  if  not  precise  data  be  obtained. 

The  value  of  comparative  tests  made  with  steam  motors  would 
perhaps  be  impaired  by  the  variations  of  the  power  coming  from 
different  conditions  of  the  flame  in  different  flights,  but  with  com- 
pressed air  or  liquid  carbonic  acid  the  comparative  tests  would 
be  useful,  to  say  the  least. 

The  seventh  subject  — the  effects  of  elasticity  in  sustaining 
surfaces  — gives  great  scope  to  experimenters.  Those  who 
devote  themselves  to  it  can  surely  help  to  answer  the  still  un- 
answered question.  Does  the  feather  structure  of  a bird’s  wing 
give  to  it  a certain  quality  which  makes  it  a better  model  for  us 
to  follow  than  the  featherless  wing  of  the  bat?  To  Lilienthal 
this  seemed  to  be  an  open  question. 

I have  tried  to  make  a strong  plea  in  behalf  of  the  flying 
model.  It  seems  to  me  that,  whatever  its  limitations  may  be, 
it  can  lessen  the  risks  to  life  and  limb. 


ABBOTT  LAWRENCE  ROTCH. 


By  the  Editor. 


Abbott  Lawrence  Rotch,  of  Boston  and  Milton,  Mass., 
whose  researches  in  meteorology  are  described  in  the  follow- 
ing article,  was  born  in  Boston,  Jan.  6,  i86i. 

He  is  a graduate  of  the  Massachusetts  Institute  of  Tech- 
nology, Class  of  ’84,  Department  of  Mechanical  Engineering. 
He  was  a member  of  the  International  Jury  of  Awards  for 
Instruments  of  Precision  at  the  Paris  Exposition  of  1889  and 
was  there  created  a Chevalier  of  the  Legion  of  Honor.  In  1902 
he  received  from  the  German  Emperor  the  Order  of  the  Prus- 
sian Crown,  III.  Class,  and  in  1905  the  Order  of  the  Red 
Eagle,  III.  Class,  in  recognition  of  his  efforts  to  advance  the 
knowledge  of  the  atmosphere.  He  was  for  ten  years  an  asso- 
ciate editor  of  the  “ American  Meteorological  Journal.” 

In  1906  he  was  appointed  Professor  of  Meteorology  by 
Harvard  University.  He  is  librarian  of  the  American  Academy 
of  Arts  and  Sciences,  a trustee  of  the  Boston  Society  of 
Natural  History,  and  has  been  for  nineteen  years  a member  of 
the  Corporation  of  the  Massachusetts  Institute  of  Technology. 
He  is  a corresponding  or  honorary  member  of  various  foreign 
scientific  societies  and  a member  of  several  international 
committees. 

His  published  contributions  to  meteorological  knowledge 
have  been  very  numerous.  His  most  recent  publication  is  a 
valuable  addition  to  aeronautical  literature  ; it  is  entitled  “ The 
Conquest  of  the  Air”  (New  York,  1910). 

By  the  many  who  know  him  Professor  Rotch  is  respected 
and  admired  for  his  devotion  to  the  cause  of  science,  for  his 
generosity  in  giving  credit  to  his  assistants  and  for  his 
large-mindedness  in  using  his  funds  for  the  advancement  of 
knowledge. 

(149) 


(Written  in  1910.) 


THE  RELATION  OF  THE  WIND  TO  AERIAL  NAVIGATION. 


By  Prof.  A.  Lawrence  Rotch. 

(^Director  of  Blue  Hill  Meteorological  Observatory  I) 

In  “The  Aeronautical  Annual”  for  1896  the  author  dis- 
cussed the  mean  velocity  of  the  wind  at  different  altitudes,  the 
maximum  velocity  and  pressure,  the  inclination  and  direction 
of  the  wind  and  the  diurnal  changes  of  velocity  and  direction 
in  their  relation  to  aeronautics.  At  that  time  there  were  no 
flying-machines  and  the  dirigible  balloon  had  only  been  shown 
to  be  possible,  so  that  the  information  given  had  chiefly  a pros- 
pective value.  The  data  obtained  in  the  free  air  were  also 
comparatively  meagre,  since,  except  for  the  observations  of 
clouds  which  gave  the  direction  and  speed  of  the  higher  air  cur- 
rents, little  knowledge  was  available.  Kites  carrying  anemom- 
eters had  been  used  for  about  a year  at  Blue  Hill,^  where  the 
first  experiments  of  the  kind  took  place,  but  no  observations 
had  been  made  at  heights  greater  than  600  metres,  or  three 
times  the  height  of  the  hill. 

At  the  present  time  conditions  have  greatly  changed.  The 
advent  of  numerous  flying-machines  and  dirigible  balloons  in 
many  countries  and  their  proposed  use  in  peace  and  war  render 
a knowledge  of  the  aerial  currents  of  great  practical  impor- 
tance. The  information,  however,  has  not  been  furnished  by 
aeronauts,  but  chiefly  by  meteorologists  operating  from  the 
ground. 

In  1896  the  International  Meteorological  Conference 
assembled  in  Paris,  impressed  by  the  recent  ascensions  of 
sounding  balloons  to  great  heights  in  Europe  and  the  success 
obtained  by  kites  carrying  instruments  at  Blue  Hill  Observatory^ 


‘ See  article  entitled  The  Blue  Hill  Meteorological  Observatory. 

(150) 


Plate  XVm. 


ABBOTT  LAWRENCE  ROTCH. 

Founder  and  Director  of  the  Blue  Hill  Meteorological  Observatory. 


THE  RELATION  OF  WIND  TO  AERIAL  NAVIGATION.  ISI 


appointed  an  International  Commission  for  Scientific  Aeronau- 
tics, which  since  that  time  has  been  collecting  data  in  the  free  air. 
Besides  several  observatories  where  this  is  done  daily,  at  some 
twenty-five  places  on  land  and  sea  throughout  the  world  observa- 
tions are  made  with  balloons  and  kites  on  one  or  more  specified 
days  each  month.  These  observations  are  centralized  and  pub- 
lished at  Strassburg,  and  while  primarily  intended  for  the  eluci- 
dation of  atmospheric  laws,  much  of  the  data  are  of  value  for 
aerial  navigation.  Blue  Hill  Observatory  is  the  oldest  of  these 
aerological  stations  and  the  data  quoted  in  this  article,  which, 
except  for  the  ocean,  pertain  to  the  eastern  United  States,  have 
been  collected  by  its  staff.  A discussion  of  the  wind  observa- 
tions obtained  at  Blue  Hill  and  St.  Louis  has  lately  been  made 
by  Mr.  A.  H.  Palmer,  and  some  of  his  figures  are  cited. 

Methods  of  Investigation.  — In  order  to  obtain  consecu- 
tive observations  at  a uniform  height  for  a considerable  period, 
it  is  necessary  that  they  shall  be  made  at  a fixed  station. 
Formerly  it  was  thought  that  the  conditions  on  a mountain- 
summit  were  the  same  as  those  at  an  equal  height  in  the  free 
air,  but  it  is  now  recognized  that  both  temperature  and  wind  are 
much  influenced  by  the  mass  of  the  mountain,  the  wind  being 
often  accelerated  just  above  the  obstacle,  like  water  passing  over 
a dam.  By  sending  anemometers  attached  to  kites  frequently  to 
or  above  the  desired  level,  the  velocity  for  a day  or  a year  has 
been  approximately  determined  at  Blue  Hill  to  3600  metres, 
and  occasionally  observations  are  elsewhere  made  up  to  6000 
metres,  or  3I  miles.  Clouds  measured  trigonometrically  from 
the  ends  of  a base-line  permit  the  direction  and  velocity  of  the 
air-currents  in  which  they  float  to  be  ascertained  to  a height  of 
10,000  metres,  or  6\  miles.  But  this  method  of  ascertaining 
the  upper  air  currents  is  not  always  available,  for  frequently 
there  are  no  clouds,  or  the  lower  strata  obscure  the  upper 
clouds,  and,  in  any  case,  the  air-currents  at  successive  heights 
can  never  be  measured  at  the  same  time.  This,  however,  can 
be  done  in  clear  weather  by  pilot-balloons,  triangulated  like  the 
clouds  from  a base-line,  or  from  a single  station  if  the  rate  of 


152 


THE  AERONAUTICAL  ANNUAL. 


ascent  be  known.  It  is  believed  that  the  first  exact  measure- 
ments in  America  of  pilot-balloons  were  made  at  Blue  Hill  in 
1909,  and  once  a balloon  was  observed  there  until  it  had  risen 
18,000  metres,  or  more  than  ii  miles.  Even  in  cloudy 
weather,  or  at  night,  it  is  possible  to  obtain  the  general  drift  of 
the  atmosphere  up  to  heights  of  16,000  metres  (10  miles),  or 
higher,  by  the  so-called  “ sounding-balloons  ” which  carry 
automatic  instruments  that  record  continuously  height,  tem- 
perature, and  the  time.  The  first  balloons  of  this  kind  in 
America  were  sent  up  from  St.  Louis  in  1904  by  the  Blue  Hill 
staff,  and  when  they  fell  to  the  ground  a hundred  miles  or  more 
away,  almost  all  were  found  and  returned  to  the  Observatory. 
Knowing  the  place  at  which  the  balloon  falls  and  having  an 
automatic  record  of  the  height  and  duration  of  the  flight,  its 
average  height,  direction,  and  speed  could  be  calculated.  As 
the  balloons  drift  towards  the  east  they  should  be  liberated 
from  the  interior  of  the  country,  and  therefore  St.  Louis  was 
chosen  for  most  of  these  experiments.  But  sounding-balloons 
can  be  used  at  sea,  provided  two  are  coupled  together,  for 
when  one  bursts  and  the  system  falls  to  the  water,  the  other 
balloon  supports  the  instrument  and  serves  as  a beacon  to 
guide  the  steamer  to  its  rescue.  Both  pilot  and  sounding- 
balloons  and  also  kites  were  employed  on  board  a steam  yacht 
sent  by  M.  Teisserenc  de  Bort  and  the  writer  to  explore  the 
atmosphere  above  the  tropical  Atlantic  in  1905-6. 

Results  of  Observations.  — First  we  will  consider  the 
increase  of  wind  with  altitude,  deduced  from  the  various 
methods  of  observation  described.  Blue  Hill  (200  metres)  has 
a mean  velocity  for  the  year  of  7.1  metres  per  second  (15.8 
miles  per  hour).  The  increase  of  velocity  is  fastest  just  above 
the  hill,  but  the  increase  continues  to  the  greatest  heights. 
The  averages  for  the  year  at  various  heights  are  as  follows:  550 
metres,  or  one-third  of  a mile  above  sea-level,  9.8  metres  per 
second,  or  21.8  miles  per  hour;  looo  metres,  10.7  metres  per 
second;  2500  metres,  12.5  metres  per  second;  3500  metres, 
15.5  metres  per  second;  5400  metres,  24.9  metres  per  second; 


THE  RELATION  OF  WIND  TO  AERIAL  NAVIGATION.  1 53 


6400  metres,  27.1  metres  per  second,  and  9500  metres  (6 
miles),  35.8  metres  per  second,  or  80.8  miles  per  hour.  The 
annual  range  from  summer  to  winter  increases  extremely  with 
height  as  shown  by  the  following  table : 

Height  in  metres 200-1000  1000-3000  3000-5000  5000-7000  7000-9000 

Mean  vel.  in  summer,  m.p.s.  ..  7.5  8.2  10.6  19. i 23.5 

Mean  vel.  in  winter,  m.p.s.  ...  8.8  14.7  21.6  49.3  54.0 

From  this  it  will  be  seen  that  the  velocity  of  the  upper  winds 
in  winter  is  more  than  double  the  rate  in  summer  and,  in  fact, 
sometimes  exceeds  100  metres  per  second,  or  223  miles  an 
hour.  The  wind-velocity  increases  nearly  twice  as  fast  at  night 
as  in  the  day-time  up  to  about  500  metres,  or  one-third  of  a 
mile.  Above  that  height  there  is  a decrease  of  velocity,  except 
in  winter,  up  to  1000  metres  and  then  the  steady  increase 
which  has  been  noted.  The  diurnal  variation  of  wind-velocity 
is  well  known  at  low  levels  on  land,  where  the  highest  velocity 
occurs  in  the  afternoon  and  the  least  velocity  in  the  early 
morning,  but  it  is  not  generally  known  that  these  conditions 
are  completely  reversed  in  the.  free  air  at  the  height  of  500 
metres,  where  the  maximum  wind  is  at  night,  as  already  stated. 

It  is  obvious  that  over  the  temperate  regions  of  the  globe  the 
surface-winds  are  constantly  changing  their  direction  as  they 
blow  around  the  passing  areas  of  high  and  low  barometric  pres- 
sures. Above  these  shifting  winds  the  wind  is  generally 
westerly,  as  proved  by  the  drift  of  the  upper  clouds  and  by 
the  balloons  sent  off  from  St.  Louis,  whose  mean  direction 
above  the  height  of  a mile  was  from  the  west-northwest. 
Whatever  the  direction  of  the  surface-wind,  it  had  a tendency 
to  become  westerly  at  a height  of  a couple  of  thousand  metres, 
a wind  from  a southerly  quarter  generally  turning  in  a right- 
handed  direction,  whereas  a wind  from  the  north  turned  to  the 
left-hand.  In  the  tropics  the  wind  blows  steadily  from  the 
northeast,  north  of  the  Equator,  and  from  the  southeast  south 
of  it,  and  it  has  been  assumed  that  above  these  winds  counter- 
trades blew  in  the  opposite  directions  in  order  that  the  atmos- 
pheric circulation  might  be  completed.  The  Franco-American 
expedition  already  mentioned  confirmed  the  theory.  Above 


154 


THE  AERONAUTICAL  ANNUAL. 


the  northeast  trade  the  wind  gradually  turned  until  it  became 
southwest  and  above  the  southeast  trade  there  was  found  an 
overlying  northwest  wind.  The  turning  was  usually  in  the 
direction  of  the  hands  of  a clock,  but  sometimes  in  the  opposite 
direction,  and  the  height  at  which  it  occurred  varied  from  a few 
hundred  to  several  thousand  metres.  Above  the  Equator  the 
wind  was  from  the  east  at  all  heights. 

Practical  Applications.  — Since  the  winds  above  the 
earth’s  surface  blow  much  faster  than  the  surface  winds,  and 
aerial  machines  are  enormously  more  bulky  than  aquatic 
vehicles  of  the  same  carrying  capacity,  it  is  evident  that  the 
currents  in  the  various  levels  of  the  atmosphere  are  of  vastly 
more  importance  to  the  aeronaut  than  are  the  ocean  currents  or 
surface-winds  to  the  sailor.  Moreover,  a balloon  or  flying- 
machine,  wholly  immersed  in  one  medium,  cannot  tack,  as  a 
ship,  floating  in  the  water,  can  advance  partly  into  the  wind. 
Consequently  a balloon  without  motive  power  can  only  drift 
with  the  current  and  a dirigible  balloon  or  flying-machine  must 
possess  a proper  speed  superior  to  that  of  the  current  in  which 
it  floats  in  order  to  make  headway  against  it.  Hence  the 
necessity  in  the  case  of  the  aerostat,  and  the  advisability  in 
the  case  of  airship  or  aeronat,  to  seek  a favorable  current  in 
the  aerial  ocean.  As  this  may  lie  at  a considerable  height,  the 
aerostat  is  best  able  to  rise  into  it,  since,  as  yet,  airship  and 
aeronat  are  limited  to  heights  of  about  a mile.  Probably  no 
aircraft  will  be  able  to  stem  the  tremendous  velocities  of  the 
higher  currents,  although  the  diminished  density  of  the  air 
reduces  its  pressure.  Thus  an  increase  of  velocity  from  9 
metres  per  second  to  54  metres  per  second  means  an  increase 
of  pressure  per  square  metre  from  5 kilograms  to  210  kilo- 
grams, but  the  actual  pressure  of  this  wind  would  be  only 
78  kilograms  at  a height  of  8000  metres.  The  supporting 
power  of  the  air  is  reduced  in  the  same  ratio,  and  since  the 
resistance  to  propulsion  against  the  average  wind  at  any  height 
increases  faster  than  the  density  diminishes,  it  follows  that, 
unless  a favorable  current  can  be  found,  navigation  at  low  levels 
is  preferable.  Near  the  ground  the  wind  is  more  gusty  on 


THE  RELATION  OF  WIND  TO  AERIAL  NAVIGATION.  1 55 


account  of  the  obstacles  which  it  encounters,  and  at  night? 
when  there  are  no  ascending  currents  or  changes  of  tempera- 
ture, a suitable  level  for  aerial  navigation  in  summer  is  at  the 
height  of  1000  metres,  this  being  a region  of  little  wind  and  of 
relative  warmth  and  dryness.  In  the  daytime  it  is  necessary  to 
ascend  above  the  cumulus  clouds  which  mark  the  limit  of  the 
convectional  currents.  Supposing  an  aircraft  to  possess  the 
very  moderate  speed  of  9 metres  per  second,  or  20  miles  per 
hour,  it  would  be  truly  dirigible  at  low-levels  in  the  vicinity  of 
Boston  on  one  day  in  two  during  the  winter  half-year  and  on 
five  days  in  six  during  the  summer  season.^  Except  for  the 
local  sea-breezes  on  our  coasts  in  summer,  the  surface-winds 
in  these  latitudes  are  too  variable  to  be  of  practical  use  in 
aerial  navigation,  but,  given  aircraft  which  can  ascend  into  the 
so-called  planetary  winds  at  a height  of  3000  or  4000  metres 
and  remain  in  the  air  for  several  days,  certain  high-level  inter- 
national routes  appear  available.  For  instance,  a spherical 
balloon,  or  better  a balloon  with  motive  power,  which  can  fulfil 
these  conditions  should  be  able  to  cross  the  American  continent 
from  west  to  east  and  even  the  Atlantic  Ocean  at  a speed  of 
not  less  than  15  metres  per  second  from  the  drift  alone.  By 
utilizing  the  northeast  surface  trade-wind  and  starting  from  the 
coast  of  Northern  Africa  or  the  adjacent  islands,  the  return 
passage  could  be  made  to  the  West  Indies  at  the  rate  of  about 
12  metres  per  second,  supposing  no  motive  power  were  used. 
By  ascending  sufficiently  high  the  southwest  counter-trade  would 
probably  furnish  an  “ air-lane  ” to  the  eastward  between  the 
West  Indies  and  Teneriffe  or  Madeira.  It  may  be  supposed 
that  the  International  Commission  for  Scientific  Aeronautics  by 
its  cooperative  work  in  the  interest  of  science  has  already 
accumulated  sufficient  data  to  chart  aerial  routes,  comparable 
to  the  ocean  routes  laid  down  by  the  various  hydrographic 
offices,  and  in  this  era  of  aerial  navigation  it  is  certain  that  the 
researches  of  such  aerological  stations  as  Mount  Weather  and 
Blue  Hill,  in  America,  and  Trappes  and  Lindenberg,  in  Europe, 
will  have  a great  practical  value. 

1 If  the  speed  be  increased  to  30  miles  per  hour,  there  will  only  be  about  30  days  in 
winter  when  the  aerial  vehicle  cannot  be  propelled  in  any  direction. 


1910.  Note.  — The  two  following  articles,  first  printed  in  “Nicholson’s  Jour- 
nal,’’ November,  1809,  and  February,  1810,  and  reprinted  in  The  Aeronautical 
Annual  for  1895,  are  especially  interesting  as  showing  that  even  at  that  time  there 
was  at  least  one  man  who  was  intelligently  experimenting  and  giving  careful  thought 
and  study  to  the  subject  of  aviation.  — Ed. 


ON  AERIAL  NAVIGATION. 


By  Sir  George  Cayley,  Bart. 

Brompton,  Sept.  6,  1809. 

Sir,  I observed  in  your  Journal  for  last  month,  that  a watch- 
maker at  Vienna,  of  the  name  of  Degen,  has  succeeded  in  raising 
himself  in  the  air  by  mechanical  means.  I waited  to  receive 
your  present  number,  in  expectation  of  seeing  some  farther  ac- 
count of  this  experiment,  before  I commenced  transcribing  the 
following  essay  upon  aerial  navigation,  from  a number  of  mem- 
oranda which  I have  made  at  various  times  upon  this  subject. 
I am  induced  to  request  your  publication  of  this  essay,  because 
I conceive,  that,  in  stating  the  fundamental  principles  of  this  art, 
together  with  a considerable  number  of  facts  and  practical  ob- 
servations, that  have  arisen  in  the  course  of  much  attention  to 
this  subject,  I may  be  expediting  the  attainment  of  an  object, 
that  will  in  time  be  found  of  great  importance  to  mankind ; so 
much  so,  that  a new  aera  in  society  will  commence,  from  the 
moment  that  aerial  navigation  is  familiarly  realized. 

It  appears  to  me,  and  I am  more  confirmed  by  the  success  of 
the  ingenious  Mr.  Degen,  that  nothing  more  is  necessary,  in 
order  to  bring  the  following  principles  into  common  practical 
use,  than  the  endeavours  of  skilful  artificers,  who  may  vary  the 
means  of  execution,  till  those  most  convenient  are  attained. 

Since  the  days  of  Bishop  Wilkins  the  scheme  of  flying  by 
artificial  wings  has  been  much  ridiculed ; and  indeed  the  idea 
of  attaching  wings  to  the  arms  of  a man  is  ridiculous  enough, 
as  the  pectoral  muscles  of  a bird  occupy  more  than  tu’o-thirds 
of  its  whole  muscular  strength,  whereas  in  man  the  muscles, 
that  could  operate  upon  wings  thus  attached,  would  probably 

(156) 


CAYLEY  ON  AERIAL  NAVIGATION. 


157 


not  exceed  one-tenth  of  his  whole  mass.  There  is  no  proof 
that,  weight  for  weight,  a man  is  comparatively  weaker  than  a 
bird ; it  is  therefore  probable,  if  he  can  be  made  to  exert  his 
whole  strength  advantageously  upon  a light  surface  similarly 
proportioned  to  his  weight  as  that  of  the  wing  to  the  bird,  that 
he  would  fly  like  the  bird,  and  the  ascent  of  Mr.  Degen  is  a 
sufficient  proof  of  the  truth  of  this  statement. 

The  flight  of  a strong  man  by  great  muscular  exertion,  though 
a curious  and  interesting  circumstance,  in  as  much  as  it  will 
probably  be  the  first  means  of  ascertaining  this  power,  and  sup- 
plying the  basis  whereon  to  improve  it,  would  be  of  little  use. 
I feel  perfectly  confident,  however,  that  this  noble  art  will  soon 
be  brought  home  to  man’s  general  convenience,  and  that  we 
shall  be  able  to  transport  ourselves  and  families,  and  their  goods 
and  chattels,  more  securely  by  air  than  by  water,  and  with  a 
velocity  of  from  20  to  100  miles  per  hour. 

To  produce  this  effect,  it  is  only  necessary  to  have  a first 
mover,  which  will  generate  more  power  in  a given  time,  in  pro- 
portion to  its  weight,  than  the  animal  system  of  muscles. 

The  consumption  of  coal  in  a Boulton  and  Watt’s  steam 
engine  is  only  about  5|-  lbs.  per  hour  for  the  power  of  one 
horse.  The  heat  produced  by  the  combustion  of  this  portion 
of  inflammable  matter  is  the  sole  cause  of  the  power  generated ; 
but  it  is  applied  through  the  intervention  of  a weight  of  water 
expanded  into  steam,  and  a still  greater  weight  of  cold  water  to 
condense  it  again.  The  engine  itself  likewise  must  be  massy 
enough  to  resist  the  whole  external  pressure  of  the  atmosphere, 
and  therefore  is  not  applicable  to  the  purpose  proposed. 
Steam  engines  have  lately  been  made  to  operate  by  expansion 
only,  and  those  might  be  constructed  so  as  to  be  light  enough 
for  this  purpose,  provided  the  usual  plan  of  a large  boiler  be 
given  up,  and  the  principle  of  injecting  a proper  charge  of  water 
into  a mass  of  tubes,  forming  the  cavity  for  the  fire,  be  adopted 
in  lieu  of  it.  The  strength  of  vessels  to  resist  internal  pressure 
being  inversely  as  their  diameters,  very  slight  metallic  tubes 
would  be  abundantly  strong,  whereas  a large  boiler  must  be  of 
great  substance  to  resist  a strong  pressure.  The  following 


158 


THE  AERONAUTICAL  ANNUAL. 


estimate  will  show  the  probable  weight  of  such  an  engine  with 
its  charge  for  one  hour. 

lb. 

The  engine  itself  from  90  to  . . . . . .100 

Weight  of  inflamed  cinders  in  a cavity  presenting  about 
4 feet  surface  of  tube  . . . . . . -25 

Supply  of  coal  for  one  hour  ......  6 

Water  for  ditto,  allowing  steam  of  one  atmosphere  to  be 
TFo'o  specific  gravity  of  water  . . . .32 


163 

I do  not  propose  this  statement  in  any  other  light  than  as  a 
rude  approximation  to  truth,  for  as  the  steam  is  operating  under 
the  disadvantage  of  atmospheric  pressure,  it  must  be  raised  to 
a higher  temperature  than  in  Messrs.  Boulton  and  Watt’s  en- 
gine ; and  this  will  require  more  fuel ; but  if  it  take  twice  as 
much,  still  the  engine  would  be  sufficiently  light,  for  it  would 
be  exerting  a force  equal  to  raising  550  lb.  one  foot  high 
per  second,  which  is  equivalent  to  the  labour  of  six  men, 
whereas  the  whole  weight  does  not  much  exceed  that  of  one 
man. 

It  may  seem  superfluous  to  inquire  farther  relative  to  first 
movers  for  aerial  navigation ; but  lightness  is  of  so  much 
value  in  this  instance,  that  it  is  proper  to  notice  the  proba- 
bility that  exists  of  using  the  expansion  of  air  by  the  sudden 
combustion  of  inflammable  powders  or  fluids  with  great  ad- 
vantage. The  French  have  lately  shown  the  great  power 
produced  by  igniting  inflammable  powders  in  close  vessels ; 
and  several  years  ago  an  engine  was  made  to  work  in  this 
country  in  a similar  manner,  by  the  inflammation  of  spirit 
of  tar.  I am  not  acquainted  with  the  name  of  the  person 
who  invented  and  obtained  a patent  for  this  engine,  but  from 
some  minutes  with  which  I was  favoured  by  Mr.  William 
Chapman,  civil  engineer  in  Newcastle,  I find  that  80  drops 
of  the  oil  of  tar  raised  eight  hundred  weight  to  the  height 
of  22  inches;  hence  a one  horse  power  may  consume  from 


eR0V««  €.  BERGDOLL 


CAYLEY  ON  AERIAL  NAVIGATION.  1 59 

10  to  12  pounds  per  hour,  and  the  engine  itself  need  not 
exceed  50  pounds  weight.  I am  informed  by  Mr.  Chapman, 
that  this  engine  was  exhibited  in  a working  state  to  Mr. 
Rennie,  Mr.  Edmund  Cartwright,  and  several  other  gentle- 
men, capable  of  appreciating  its  powers;  but  that  it  was 
given  up  in  consequence  of  the  expense  attending  its  con- 
sumption being  about  eight  times  greater  than  that  of  a 
steam  engine  of  the  same  force. 

Probably  a much  cheaper  engine  of  this  sort  might  be 
produced  by  a gas-light  apparatus,  and  by  firing  the  inflam- 
mable air  generated,  with  a due  portion  of  common  air, 
under  a piston.  Upon  some  of  these  principles  it  is  perfectly 
clear,  that  force  can  be  obtained  by  a much  lighter  apparatus 
than  the  muscles  of  animals  or  birds,  and  therefore  in  such 
proportion  may  aerial  vehicles  be  loaded  with  inactive  matter. 
Even  the  expansion  steam  engine  doing  the  work  of  six 
men,  and  only  weighing  equal  to  one,  will  as  readily  raise 
five  men  into  the  air,  as  Mr.  Degen  can  elevate  himself  by 
his  own  exertions ; but  by  increasing  the  magnitude  of  the 
engine,  10,  50,  or  500  men  may  equally  well  be  conveyed; 
and  convenience  alone,  regulated  by  the  strength  and  size  of 
materials,  will  point  out  the  limit  for  the  size  of  vessels  in 
aerial  navigation. 

Having  rendered  the  accomplishment  of  this  object  prob- 
able upon  the  general  view  of  the  subject,  I shall  proceed 
to  point  out  the  principles  of  the  art  itself.  For  the  sake 
of  perspicuity  I shall,  in  the  first  instance,  analyze  the  most 
simple  action  of  the  wing  in  birds,  although  it  necessarily 
supposes  many  previous  steps.  When  large  birds,  that  have 
a considerable  extent  of  wing  compared  with  their  weight, 
have  acquired  their  full  velocity,  it  may  frequently  be  observed, 
that  they  extend  their  wings,  and  without  waving  them,  con- 
tinue to  skim  for  some  time  in  a horizontal  path.  Fig.  i, 
in  the  Plate,  represents  a bird  in  this  act. 

Let  a 3 he  a section  of  the  plane  of  both  wings  opposing 
the  horizontal  current  of  the  air  (created  by  its  own  motion) 
which  may  be  represented  by  the  line  c d,  and  is  the  meas- 


l6o  THE  AERONAUTICAL  ANNUAL. 

ure  of  the  velocity  of  the  bird.  The  angle  b d c can  be  in- 
creased at  the  will  of  the  bird,  and  to  preserve  a perfectly 
horizontal  path,  without  the  wing  being  waved,  must  con- 
tinually be  increased  in  a complete  ratio,  (useless  at  present 
to  enter  into)  till  the  motion  is  stopped  altogether;  but  at 
one  given  time  the  position  of  the  wings  may  be  truly  rep- 
resented by  the  angle  b d c.  Draw  d e perpendicular  to 
the  plane  of  the  wings,  produce  the  line  ^ as  far  as  re- 
quired, and  from  the  point  e,  assumed  at  pleasure  in  the 
line  d e,  let  fall  e f perpendicular  to  d f.  Then  d e will 
represent  the  whole  force  of  the  air  under  the  wing;  which 
being  resolved  into  the  two  forces  e f and  f d,  the  former 
represents  the  force  that  sustains  the  weight  of  the  bird,  the 
latter  the  retarding  force  by  which  the  velocity  of  the  motion, 
producing  the  currents  d,  will  continually  be  diminished.  ef\% 
always  a known  quantity,  being  equal  to  the  weight  of  the  bird, 
and  hence  f d \?>  also  known,  as  it  will  always  bear  the  same 
proportion  to  the  weight  of  the  bird,  as  the  sine  of  the  angle 
b d e bears  to  its  cosine,  the  angles  d e f,  and  b d c,  being 
equal.  In  addition  to  the  retarding  force  thus  received  is  the 
direct  resistance,  which  the  bulk  of  the  bird  opposes  to  the  cur- 
rent. This  is  a matter  to  be  entered  into  separately  from  the 
principle  now  under  consideration;  and  for  the  present  may  be 
wholly  neglected,  under  the  supposition  of  its  being  balanced 
by  a force  precisely  equal  and  opposite  to  itself. 

Before  it  is  possible  to  apply  this  basis  of  the  principle  of 
flying  in  birds  to  the  purposes  of  aerial  navigation,  it  will  be 
necessary  to  encumber  it  with  a few  practical  observations. 
The  whole  problem  is  confined  within  these  limits,  viz.  To 
make  a surface  support  a given  weight  by  the  application  of 
power  to  the  resistance  of  air.  Magnitude  is  the  first  question 
respecting  the  surface.  Many  experiments  have  been  made 
upon  the  direct  resistance  of  air,  by  Mr.  Robins,  Mr.  Rouse, 
Mr.  Edgeworth,  Mr.  Smeaton,  and  others.  The  result  of  Mr. 
Smeaton’s  experiments  and  observations  was,  that  a surface  of 
a square  foot  met  with  a resistance  of  one  pound,  when  it  trav- 
elled perpendicularly  to  itself  through  air  at  a \-elocity  of  2i 


CAYLEY  ON  AERIAL  NAVIGATION. 


i6i 


IKeholsanHir  I^dlof  Jcumcd/  Vbhk)LLV.I’L.  6 pJ'J^- 


i62 


THE  AERONAUTICAL  ANNUAL, 


feet  per  second.  I have  tried  many  experiments  upon  a large 
scale  to  ascertain  this  point.  The  instrument  was  similar  to 
that  used  by  Mr.  Robins,  but  the  surface  used  was  larger, 
being  an  exact  square  foot,  moving  round  upon  an  arm  about 
five  feet  long,  and  turned  by  weights  over  a pulley.  The  time 
was  measured  by  a stop  watch,  and  the  distance  travelled  over 
in  each  experiment  was  600  feet.  I shall  for  the  present  only 
give  the  result  of  many  carefully  repeated  experiments,  which 
is,  that  a velocity  of  11.538  feet  per  second  generated  a resist- 
ance of  4 ounces;  and  that  a velocity  of  17.16  feet  per  second 
gave  8 ounces  resistance.  This  delicate  instrument  would  have 
beon  strained  by  the  additional  weight  necessary  to  have  tried 
the  velocity  generating  a pressure  of  one  pound  per  square  foot ; 
but  if  the  resistance  be  taken  to  vary  as  the  square  of  the 
velocity,  the  former  will  give  the  velocity  necessary  for  this  pur- 
pose at  23.1  feet,  the  latter  24.28  per  second.  I shall  therefore 
take  23.6  feet  as  somewhat  approaching  the  truth. 

Having  ascertained  this  point,  had  our  tables  of  angular  re- 
sistance been  complete,  the  size  of  the  surface  necessary  for 
any  given  weight  would  easily  have  been  determined.  Theory', 
which  gives  the  resistance  of  a surface  opposed  to  the  same 
current  in  different  angles,  to  be  as  the  squares  of  the  sine  of 
the  angle  of  incidence,  is  of  no  use  in  this  case ; as  it  appears 
from  the  experiments  of  the  French  Academy,  that  in  acute 
angles,  the  resistance  varies  much  more  nearly  in  the  direct 
ratio  of  the  sines,  than  as  the  squares  of  the  sines  of  the  angles 
of  incidence.  The  flight  of  birds  will  prove  to  an  attentive 
observer,  that,  with  a concave  wing  apparently  parallel  to  the 
horizontal  path  of  the  bird,  the  same  support,  and  of  course 
resistance,  is  obtained.  And  hence  I am  inclined  to  suspect, 
that,  under  extremely  acute  angles,  with  concave  surfaces,  the 
resistance  is  nearly  similar  in  them  all.  I conceive  the  opera- 
tion may  be  of  a different  nature  from  what  takes  place  in  larger 
angles,  and  may  partake  more  of  the  principle  of  pressure  ex- 
hibited in  the  instrument  known  by  the  name  of  the  hydro- 
static paradox,  a slender  filament  of  the  current  is  constantly 
received  under  the  anterior  edge  of  the  surface,  and  directed 


CAYLEY  ON  AERIAL  NAVIGATION.  163 

upward  into  the  cavity,  by  the  filament  above  it,  in  being 
obliged  to  mount  along  the  convexity  of  the  surface,  having 
created  a slight  vacuity  immediately  behind  the  point  of  sep- 
aration. The  fluid  accumulated  thus  within  the  cavity  has  to 
make  its  escape  at  the  posterior  edge  of  the  surface,  where  it  is 
directed  considerably  downward ; and  therefore  has  to  overcome 
and  displace  a portion  of  the  direct  current  passing  with  its  full 
velocity  immediately  below  it;  hence  whatever  elasticity  this 
effort  requires  operates  upon  the  whole  concavity  of  the  surface, 
excepting  a small  portion  of  the  anterior  edge.  This  may  or 
may  not  be  the  true  theory,  but  it  appears  to  me  to  be  the 
most  probable  account  of  a phenomenon,  which  the  flight  of 
birds  proves  to  exist. 

Six  degrees  was  the  most  acute  angle,  the  resistance  of 
which  was  determined  by  the  valuable  experiments  of  the 
French  Academy;  and  it  gave  iV  of  the  resistance,  which 
the  same  surface  would  have  received  from  the  same  cur- 
rent when  perpendicular  to  itself.  Hence  then  a superficial 
foot,  forming  an  angle  of  six  degrees  with  the  horizon, 
would,  if  carried  forward  horizontally  (as  a bird  in  the  act 
of  skimming)  with  a velocity  of  23.6  feet  per  second,  re- 
ceive a pressure  of  tV  of  a pound  perpendicular  to  itself. 
And,  if  we  allow  the  resistance  to  increase  as  the  square  of 
the  velocity,  at  27.3  feet  per  second  it  would  receive  a 
pressure  of  one  pound.  I have  weighed  and  measured  the 
surface  of  a great  many  birds,  but  at  present  shall  select 
the  common  rook  {corvus  frugilegus')  because  its  surface 
and  weight  are  as  nearly  as  possible  in  the  ratio  of  a super- 
ficial foot  to  a pound.  The  flight  of  this  bird,  during  any 
part  of  which  they  can  skim  at  pleasure,  is  (from  an  aver- 
age of  many  observations)  about  34.5  feet  per  second. 
The  concavity  of  the  wing  may  account  for  the  greater  re- 
sistance here  received,  than  the  experiments  upon  plain 
surfaces  would  indicate.  I am  convinced,  that  the  angle 
made  use  of  in  the  crow’s  wing  is  much  more  acute  than 
six  degrees ; but  in  the  observations,  that  will  be  grounded 
upon  these  data,  I may  safely  state,  that  every  foot  of  such 


1 64  the  aeronautical  annual. 

curved  surface,  as  will  be  used  in  aerial  navigation,  will  re- 
ceive a resistance  of  one  pound,  perpendicular  to  itself, 
when  carried  through  the  air  in  an  angle  of  six  degrees  with 
the  line  of  its  path,  at  a velocity  of  about  34  or  35  feet  per 
second. 

Let  a b,  fig.  2,  represent  such  a surface  or  sail  made  of 
thin  cloth,  and  containing  about  200  square  feet  (if  of  a 
square  form  the  side  will  be  a little  more  than  14  feet)  ; and 
the  whole  of  a firm  texture.  Let  the  weight  of  the  man  and 
the  machine  be  200  pounds.  Then  if  a current  of  wind 
blew  in  the  direction  c d,  with  a velocity  of  35  feet  per  sec- 
ond, at  the  same  time  that  a cord  represented  c d would 
sustain  a tension  of  2 r pounds,  the  machine  would  be  sus- 
pended in  the  air,  or  at  least  be  within  a few  ounces  of  it 
(falling  short  of  such  support  only  in  the  ratio  of  the  sine 
of  the  angle  of  94  degrees  compared  with  radius ; to  bal- 
ance which  defect,  suppose  a little  ballast  to  be  thrown  out) 
for  the  line  d e represents  a force  of  200  pounds,  which,  as 
before,  being  resolved  into  d f and  f e,  the  former  will  rep- 
resent the  resistance  in  the  direction  of  the  current,  and 
the  latter  that  which  sustains  the  weight  of  the  machine. 
It  is  perfectly  indifferent  whether  the  wind  blow  against  the 
plane,  or  the  plane  be  driven  with  an  equal  velocity  against 
the  air.  Hence,  if  this  machine  were  pulled  along  by  a 
cord  c d,  with  a tension  of  about  21  pounds,  at  a velocity 
of  35  feet  per  second,  it  would  be  suspended  in  a horizontal 
path;  and  if  in  lieu  of  this  cord  any  other  propelling  power 
were  generated  in  this  direction,  with  a like  intensity,  a sim- 
ilar effect  would  be  produced.  If  therefore  the  waft  of 
surfaces  advantageously  moved,  by  any  force  generated 
within  the  machine,  took  place  to  the  extent  required,  aerial 
navigation  would  be  accomplished.  As  the  acuteness  of  the 
angle  between  the  plane  and  current  increases,  the  propel- 
ling power  required  is  less  and  less.  The  principle  is  simi- 
lar to  that  of  the  inclined  plane,  in  which  theoretically  one 
pound  may  be  made  to  sustain  all  but  an  infinite  quantity; 
for  in  this  case,  if  the  magnitude  of  the  surface  be  increased 


CAYLEY  ON  AERIAL  NAVIGATION.  1 65 

ad  infinitum,  the  angle  with  the  current  may  be  diminished, 
and  consequently  the  propelling  force,  in  the  same  ratio. 
In  practice,  the  extra  resistance  of  the  car  and  other  parts 
of  the  machine,  which  consume  a considerable  portion  of 
power,  will  regulate  the  limits  to  which  this  principle,  which 
is  the  true  basis  of  aerial  navigation,  can  be  carried ; and 
the  perfect  ease  with  which  some  birds  are  suspended  in 
long  horizontal  flights,  without  one  waft  of  their  wings,  en- 
courages the  idea,  that  a slight  power  only  is  necessary. 

As  there  are  many  other  considerations  relative  to  the  practi- 
cal introduction  of  this  machine,  which  would  occupy  too  much 
space  for  any  one  number  of  your  valuable  Journal,  I pro- 
pose, with  your  approbation,  to  furnish  these  in  your  subse- 
quent numbers  ; taking  this  opportunity  to  observe,  that  perfect 
steadiness,  safety,  and  steerage,  I have  long  since  accomplished 
upon  a considerable  scale  of  magnitude ; and  that  I am  engaged 
in  making  some  farther  experiments  upon  a machine  I con- 
structed last  summer,  large  enough  for  aerial  navigation,  but 
which  I have  not  had  an  opportunity  to  try  the  effect  of,  ex- 
cepting as  to  its  proper  balance  and  security.  It  was  very 
beautiful  to  see  this  noble  white  bird  sail  majestically  from  the 
top  of  a hill  to  any  given  point  of  the  plane  below  it,  according 
to  the  set  of  its  rudder,  merely  by  its  own  weight,  descending  in 
an  angle  of  about  18  degrees  with  the  horizon.  The  exertions 
of  an  individual,  with  other  avocations,  are  extremely  inade- 
quate to  the  progress,  which  this  valuable  subject  requires. 
Every  man  acquainted  with  experiments  upon  a large  scale  well 
knows  how  leisurely  fact  follows  theory,  if  ever  so  well  founded. 
I do  therefore  hope,  that  what  I have  said,  and  have  still  to 
offer,  will  induce  others  to  give  their  attention  to  this  subject; 
and  that  England  may  not  be  backward  in  rivalling  the  conti- 
nent in  a more  worthy  contest  than  that  of  arms. 

As  it  may  be  an  amusement  to  some  of  your  readers  to  see  a 
machine  rise  in  the  air  by  mechanical  means,  I will  conclude 
my  present  communication  by  describing  an  instrument  of  this 
kind,  which  any  one  can  construct  at  the  expense  of  ten  minutes 
labour. 


1 66  THE  AERONAUTICAL  ANNUAL. 

a and  b,  fig.  3,  are  two  corks,  into  each  of  which  are  inserted 
four  wing  feathers  from  any  bird,  so  as  to  be  slightly  inclined 
like  the  sails  of  a windmill,  but  in  opposite  directions  in  each 
set.  A round  shaft  is  fixed  in  the  cork  a,  which  ends  in  a 
sharp  point.  At  the  upper  part  of  the  cork  b is  fixed  a whale- 
bone bow,  having  a small  pivot  hole  in  its  centre,  to  receive  the 
point  of  the  shaft.  The  bow  is  then  to  be  strung  equally  on 
each  side  to  the  upper  portion  of  the  shaft,  and  the  little 
machine  is  completed.  Wind  up  the  string  by  turning  the 
flyers  different  ways,  so  that  the  spring  of  the  bow  may  unwind 
them  with  their  anterior  edges  ascending ; then  place  the  cork 
with  the  bow  attached  to  it  upon  a table,  and  with  a finger  on 
the  upper  cork  press  strong  enough  to  prevent  the  string  from 
unwinding,  and  taking  it  away  suddenly,  the  instrument  will  rise 
to  the  ceiling.  This  was  the  first  experiment  I made  upon  this 
subject  in  the  year  1796.  If  in  lieu  of  these  small  feathers 
large  planes,  containing  together  200  square  feet,  were  similarly 
placed,  or  in  any  other  more  convenient  position,  and  were 
turned  by  a man,  or  first  mover  of  adequate  power,  a similar 
effect  would  be  the  consequence,  and  for  the  mere  purpose  of 
ascent  this  is  perhaps  the  best  apparatus ; but  speed  is  the 
great  object  of  this  invention,  and  this  requires  a different 
structure. 


P.  S.  In  lieu  of  applying  the  continued  action  of  the  inclined 
plane  by  means  of  the  rotative  motion  of  flyers,  the  same  princi- 
ple may  be  made  use  of  by  the  alternate  motion  of  surfaces 
backward  and  forward ; and  although  the  scanty  description 
hitherto  published  of  Mr.  Degen’s  apparatus  will  scarcely  justify 
any  conclusion  upon  the  subject;  yet  as  the  principle  above 
described  must  be  the  basis  of  every  engine  for  aerial  naviga- 
tion by  mechanical  means,  I conceive,  that  the  method  adopted 
by  him  has  been  nearly  as  follows.  Let  A and  B,  fig.  4,  be  two 
surfaces  or  parachutes,  supported  upon  the  long  shafts  C and 
D,  which  are  fixed  to  the  ends  of  the  connecting  beam  E,  by 
hinges.  At  E,  let  there  be  a convenient  seat  for  the  aeronaut. 


CAYLEY  ON  AERIAL  NAVIGATION. 


167 


and  before  him  a cross  bar  turning  upon  a pivot  in  its  centre, 
which  being  connected  with  the  shafts  of  the  parachutes  by  the 
rods  F and  G,  will  enable  him  to  work  them  alternately  back- 
ward and  forward,  as  represented  by  the  dotted  lines.  If  the 
upright  shafts  be  elastic,  or  have  a hinge  to  give  way  a little  near 
their  tops,  the  weight  and  resistance  of  the  parachutes  will  in- 
cline them  so,  as  to  make  a small  angle  with  the  direction  of 
their  motion,  and  hence  the  machine  rises.  A slight  heeling  of 
the  parachutes  toward  one  side,  or  an  alteration  in  the  position 
of  the  weight,  may  enable  the  aeronaut  to  steer  such  an  ap- 
paratus tolerably  well ; but  many  better  constructions  may  be 
formed,  for  combining  the  requisites  of  speed,  convenience  and 
steerage.  It  is  a great  point  gained,  when  the  first  experiments 
demonstrate  the  practicability  of  an  art ; and  Mr.  Degen,  by 
whatever  means  he  has  effected  this  purpose,  deserves  much 
credit  for  his  ingenuity. 


[From  Aero.  Ann.,  1S95.] 


ON  AERIAL  NAVIGATION. 


(^From  Nicholson' s yournal,  February,  18/0.') 

By  Sir  George  Cayley,  Bart. 

Having,  in  my  former  communication,  described  the  general 
principle  of  support  in  aerial  navigation,  I shall  proceed  to  show 
how  this  principle  must  be  applied,  so  as  to  be  steady  and 
manageable. 

Several  persons  have  ventured  to  descend  from  balloons  in 
what  is  termed  a parachute,  which  exactly  resembles  a large 
umbrella,  with  a light  car  suspended  by  cords  underneath  it. 

Mr.  Garnerin’s  descent  in  one  of  these  machines  will  be  in  the 
recollection  of  many ; and  I make  the  remark  for  the  purpose 
of  alluding  to  the  continued  oscillation,  or  want  of  steadiness, 
which  is  said  to  have  endangered  that  bold  aeronaut.  It  is 
very  remarkable,  that  the  only  machines  of  this  sort,  which 
have  been  constructed,  are  nearly  of  the  worst  possible  form  for 
producing  a steady  descent,  the  purpose  for  which  they  are 
intended.  To  render  this  subject  more  familiar,  let  us  recollect, 
that  in  a boat,  swimming  upon  water,  its  stability  or  stiffness 
depends,  in  general  terms,  upon  the  weight  and  distance  from 
the  centre  of  the  section  elevated  above  the  water,  by  any  gtyen 
heel  of  the  boat,  on  one  side ; and  on  the  bulk,  and  its  distance 
from  the  centre,  which  is  immersed  below  the  water,  on  the 
other  side  ; the  combined  endeavour  of  the  one  to  fall,  and  of  the 
other  to  swim,  produces  the  desired  effect  in  a well-constructed 
boat.  The  centre  of  gravity  of  the  boat  being  more  or  less  below 
the  centre  of  suspension  is  an  additional  cause  of  its  stability. 

Let  us  now  examine  the  effect  of  a parachute  represented  by 
A B,  Fig.  I,  PI.  III.  When  it  has  heeled  into  the  position  a b, 
the  side  a is  become  perpendicular  to  the  current,  created  by  the 
descent,  and  therefore  resists  with  its  greatest  power ; whereas 

(168) 


CAYLEY  ON  AERIAL  NAVIGATION. 


169 


'liiJwLsms  PWcs.JatariaL7ohIZVblJR.p.$l. 


THE  AERONAUTICAL  ANNUAL, 


170 

the  side  b is  become  more  oblique,  and  of  course  its  resistance  is 
much  diminished.  In  the  instance  here  represented,  the  angle 
of  the  parachute  itself  is  144°,  and  it  is  supposed  to  heel  18°, 
the  comparative  resistance  of  the  side  a to  the  side  b,  will  be  as 
the  square  of  the  line  a,  as  radius,  to  the  square  of  the  sine 
of  the  angle  of with  the  current;  which,  being  54  degrees, 
gives  the  resistances  nearly  in  the  ratio  of  i to  0.67 ; and  this 
will  be  reduced  to  only  0.544,  when  estimated  in  a direction  per- 
pendicular to  the  horizon.  Hence,  so  far  as  this  form  of  the  sail 
or  plane  is  regarded,  it  operates  directly  in  opposition  to  the 
principle  of  stability ; for  the  side  that  is  required  to  fall  resists 
much  more  in  its  new  position,  and  that  which  is  required  to 
rise  resists  much  less ; therefore  complete  inversion  would  be 
the  consequence,  if  it  were  not  for  the  weight  being  suspended 
so  very  much  below  the  surface,  which,  counteracting  this  ten- 
dency, converts  the  effort  into  a violent  oscillation. 

On  the  contrary,  let  the  surface  be  applied  in  the  inverted 
position,  as  represented  at  C D,  Fig.  2,  and  suppose  it  to  be 
heeled  to  the  same  angle  as  before,  represented  by  the  dotted 
lines  c d.  Here  the  exact  reverse  of  the  former  instance  takes 
place ; for  that  side,  which  is  required  to  rise,  has  gained  resist- 
ance by  its  new  position,  and  that  which  is  required  to  sink  has 
lost  it;  so  that  as  much  power  operates  to  restore  the  equi- 
librium in  this  case,  as  tended  to  destroy  it  in  the  other;  the 
operation  very  much  resembling  what  takes  place  in  the  com- 
mon boat.^ 

This  angular  form,  with  the  apex  downward,  is  the  chief  basis 
of  stability  in  aerial  navigation ; but  as  the  sheet  which  is  to 
suspend  the  weight  attached  to  it,  in  its  horizontal  path  through 
the  air,  must  present  a slightly  concave  surface  in  a small  angle 
with  the  current,  this  principle  can  only  be  used  in  the  lateral 
extension  of  the  sheet ; and  this  most  effectually  prevents  any 
rolling  of  the  machine  from  side  to  side.  Hence,  the  section  of 

* A very  simple  experiment  will  show  the  truth  of  this  theory.  Take  a circular  piece  of 
writing  paper,  and  folding  up  a small  portion,  in  the  line  of  two  radii,  it  \vill  be  formed  into 
an  obtuse  cone.  Place  a small  weight  in  the  apex,  and  letting  it  fall  from  any  height,  it 
will  steadily  preserve  that  position  to  the  ground.  Invert  it,  and,  if  the  weight  be  fixed,  like 
the  life  boat,  it  rights  itself  instantly. 


CAYLEY  ON  AERIAL  NAVIGATION.  I/I 

the  inverted  parachute,  Fig.  2,  may  equally  well  represent  the 
cross  section  of  a sheet  for  aerial  navigation. 

The  principle  of  stability  in  the  direction  of  the  path  of  the 
machine,  must  be  derived  from  a different  source.  Let  A B, 
Fig.  3,  be  a longitudinal  section  of  a sail,  and  let  C be  its  centre 
of  resistance,  which  experiment  shows  to  be  considerably  more 
forward  than  the  centre  of  the  sail.  Let  C D be  drawn  perpen- 
dicular to  A B,  and  let  the  centre  of  gravity  of  the  machine  be 
at  any  point  in  that  line,  as  at  D.  Then,  if  it  be  projected  in  a 
horizontal  path  with  velocity  enough  to  support  the  weight,  the 
machine  will  retain  its  relative  position,  like  a bird  in  the  act  of 
skimming;  for,  drawing  C E perpendicular  to  the  horizon,  and 
D E parallel  to  it,  the  line  C E will,  at  some  particular  moment, 
represent  the  supporting  power,  and  likewise  its  opponent  the 
weight ; and  the  line  D E will  represent  the  retarding  power, 
and  its  equivalent,  that  portion  of  the  projectile  force  expended 
in  overcoming  it:  hence,  these  various  powers  being  exactly 
balanced,  there  is  no  tendency  in  the  machine  but  to  proceed  in 
its  path,  with  its  remaining  portion  of  projectile  force. 

The  stability  in  this  position,  arising  from  the  centre  of 
gravity  being  below  the  point  of  suspension,  is  aided  by  a re- 
markable circumstance,  that  experiment  alone  could  point  out. 
In  very  acute  angles  with  the  current  it  appears,  that  the  centre 
of  resistance  in  the  sail  does  not  coincide  with  the  centre  of  its 
surface,  but  is  considerably  in  front  of  it.  As  the  obliquity  of 
the  current  decreases,  these  centres  approach,  and  coincide 
when  the  current  becomes  perpendicular  to  the  sail.  Hence 
any  heel  of  the  machine  backward  or  forward  removes  the  centre 
of  support  behind  or  before  the  point  of  suspension ; and  oper- 
ates to  restore  the  original  position,  by  a power,  equal  to  the 
whole  weight  of  the  machine,  acting  upon  a lever  equal  in 
length  to  the  distance  the  centre  has  removed. 

To  render  the  machine  perfectly  steady,  and  likewise  to 
enable  it  to  ascend  and  descend  in  its  path,  it  becomes  nec- 
essary to  add  a rudder  in  a similar  position  to  the  tail  in 
birds.  Let  F G be  the  section  of  such  a surface,  parallel 
to  the  current;  and  let  it  be  capable  of  moving  up  and 


1/2 


THE  AERONAUTICAL  ANNUAL. 


down  upon  G,  as  a centre,  and  of  being  fixed  in  any  posi- 
tion. The  powers  of  the  machine  being  previously  balanced, 
if  the  least  pressure  be  exerted  by  the  current,  either  upon 
the  upper  or  under  surface  of  the  rudder,  according  to  the 
will  of  the  aeronaut,  it  will  cause  the  machine  to  rise  or 
fall  in  its  path,  so  long  as  the  projectile  or  propelling  force 
is  continued  with  sufficient  energy.  From  a variety  of  ex- 
periments upon  this  subject  I find,  that,  when  the  machine 
is  going  forward  with  a superabundant  velocity,  or  that 
which  would  induce  it  to  rise  in  its  path,  a very  steady  hori- 
zontal course  is  effected  by  a considerable  depression  of 
the  rudder,  which  has  the  advantage  of  making  use  of  this 
portion  of  sail  in  aiding  the  support  of  the  weight.  When 
the  velocity  is  becoming  less,  as  in  the  act  of  alighting,  then 
the  rudder  must  gradually  recede  from  this  position,  and 
even  become  elevated,  for  the  purpose  of  preventing  the 
machine  from  sinking  too  much  in  front,  owing  to  the  com- 
bined effect  of  the  want  of  projectile  force  sufficient  to  sus- 
tain the  centre  of  gravity  in  its  usual  position,  and  of  the 
centre  of  support  approaching  the  centre  of  the  sail. 

The  elevation  and  depression  of  the  machine  are  not  the 
only  purposes,  for  which  the  rudder  is  designed.  This  ap- 
pendage must  be  furnished  with  a vertical  sail,  and  be  ca- 
pable of  turning  from  side  to  side,  in  addition  to  its  other 
movements,  which  effects  the  complete  steerage  of  the  vessel. 

All  these  principles,  upon  which  the  support,  steadiness, 
elevation,  depression,  and  steerage,  of  vessels  for  aerial 
navigation,  depend,  have  been  abundantly  verified  by  experi- 
ments both  upon  a small  and  a large  scale.  Last  year  I 
made  a machine,  having  a surface  of  300  square  feet,  which 
was  accidentally  broken  before  there  was  an  opportunity  of 
trying  the  effect  of  the  propelling  apparatus ; but  its  steer- 
age and  steadiness  were  perfectly  proved,  and  it  would  sail 
obliquely  downward  in  any  direction,  according  to  the  set 
of  the  rudder.  Even  in  this  state,  when  any  person  ran 
forward  in  it,  with  his  full  speed,  taking  advantage  of  a 
gentle  breeze  in  front,  it  would  bear  upward  so  strongly  as 


CAYLEY  ON  AERIAL  NAVIGATION, 


173 


scarcely  to  allow  him  to  touch  the  ground ; and  would 
frequently  lift  him  up,  and  convey  him  several  yards  together. 

The  best  mode  of  producing  the  propelling  power  is  the 
only  thing,  that  remains  yet  untried  toward  the  completion 
of  the  invention.  I am  preparing  to  resume  my  experiments 
upon  this  subject,  and  state  the  following  observations,  in 
the  hope  that  others  may  be  induced  to  give  their  attention 
towards  expediting  the  attainment  of  this  art. 

The  act  of  flying  is  continually  exhibited  to  our  view;  and 
the  principles  upon  which  it  is  effected  are  the  same  as  those 
before  stated.  If  an  attentive  observer  examines  the  waft  of  a 
wing,  he  will  perceive,  that  about  one  third  part,  toward  the 
extreme  point,  is  turned  obliquely  backward ; this  being  the 
only  portion,  that  has  velocity  enough  to  overtake  the  current, 
passing  so  rapidly  beneath  it,  when  in  this  unfavourable  posi- 
tion. Hence  this  is  the  only  portion  that  gives  any  propelling 
force. 

To  make  this  more  intelligible,  let  A B,  Fig.  4,  be  a section 
of  this  part  of  the  wing.  Let  C D represent  the  velocity  of  the 
bird’s  path,  or  the  current,  and  E D that  of  the  wing  in  its 
waft:  then  C E will  represent  the  magnitude  and  direction 
of  the  compound  or  actual  current  striking  the  under  surface  of 
the  wing.  Suppose  E F,  perpendicular  to  A B,  to  represent 
the  whole  pressure ; E G being  parallel  to  the  horizon,  will 
represent  the  propelling  force ; and  G F,  perpendicular  to  it, 
the  supporting  power.  A bird  is  supported  as  effectually 
during  the  return  as  during  the  beat  of  its  wing;  this  is  chiefly 
effected  by  receiving  the  resistance  of  the  current  under  that 
portion  of  the  wing  next  the  body  where  its  receding  motion 
is  so  slow  as  to  be  of  scarcely  any  effect.  The  extreme  portion 
of  the  wing,  owing  to  its  velocity,  receives  a pressure  downward 
and  obliquely  forward,  which  forms  a part  of  the  propelling 
force ; and  at  the  same  time,  by  forcing  the  hinder  part  of  the 
middle  portion  of  the  wing  downward,  so  increases  its  angle 
with  the  current,  as  to  enable  it  still  to  receive  nearly  its  usual 
pressure  from  beneath. 

As  the  common  rook  has  its  surface  and  weight  in  the  ratio 


174 


THE  AERONAUTICAL  ANNUAL. 


of  a square  foot  to  a pound,  it  may  be  considered  as  a standard 
for  calculations  of  this  sort ; and  I shall  therefore  state,  from 
the  average  of  many  careful  observations,  the  movements  of 
that  bird.  Its  velocity,  represented  by  C D,  Fig.  4,  is  34.5  feet 
per  second.  It  moves  its  wing  up  and  down  once  in  flying  over 
a space  of  12.9  feet.  Hence,  as  the  centre  of  resistance  of  the 
extreme  portion  of  the  wing  moves  over  a space  of  0.75  of  a 
foot  each  beat  or  return,  its  velocity  is  about  4 feet  per  second, 
represented  by  the  line  E D.  As  the  wing  certainly  overtakes 
the  current,  it  must  be  inclined  from  it  in  an  angle  something 
less  than  7°,  for  at  this  angle  it  would  scarcely  be  able  to  keep 
parallel  with  it,  unless  the  waft  downward  were  performed  with 
more  velocity  than  the  return ; which  may  be  and  probably  is 
the  case,  though  these  movements  appear  to  be  of  equal  dura- 
tion. The  propelling  power,  represented  by  E G,  under  these 
circumstances,  cannot  be  equal  to  an  eighth  part  of  the  support- 
ing power  G F,  exerted  upon  this  portion  of  the  wing ; yet  this, 
together  with  the  aid  from  the  return  of  the  wing,  has  to  over- 
come all  the  retarding  power  of  the  surface,  and  the  direct 
resistance  occasioned  by  the  bulk  of  the  body. 

It  has  been  before  suggested,  and  I believe  upon  good  grounds, 
that  very  acute  angles  vary  little  in  the  degree  of  resistance  they 
make  under  a similar  velocity  of  current.  Hence  it  is  probable, 
that  this  propelling  part  of  the  wing  receives  little  more  than  its 
common  proportion  of  resistance,  during  the  waft  downward. 
If  it  be  taken  at  one-third  of  the  whole  surface,  and  one-eighth 
of  this  be  allowed  as  the  propelling  power,  it  will  only  amount 
to  one  twenty-fourth  of  the  weight  of  the  bird ; and  even  this  is 
exerted  only  half  the  duration  of  the  flight.  The  power  gained 
in  the  return  of  the  wing  must  be  added,  to  render  this  state- 
ment correct,  and  it  is  difficult  to  estimate  this ; yet  the  follow- 
ing statement  proves,  that  a greater  degree  of  propelling  force 
is  obtained,  upon  the  whole,  than  the  foregoing  observations  will 
justify.  Suppose  the  largest  circle  that  can  be  described  in  the 
breast  of  a crow,  to  be  12  inches  in  area.  Such  a surface,  movdng 
at  the  velocity  of  34.5  feet  per  second,  would  meet  a resistance 
of  0.216  of  a pound,  which,  reduced  by  the  proportion  of  the 


CAYLEY  ON  AERIAL  NAVIGATION. 


175 


resistance  of  a sphere  to  its  great  circle  (given  by  Mr.  Robins 
as  I to  2.27)  leaves  a resistance  of  0.095  of  a pound,  had  the 
breast  been  hemispherical.  It  is  probable  however,  that  the 
curve  made  use  of  by  Nature  to  avoid  resistance,  being  so  ex- 
quisitely adapted  to  its  purpose,  will  reduce  this  quantity  to  one 
half  less  than  the  resistance  of  the  sphere,  which  would  ulti- 
mately leave  0.0475  of  a pound  as  somewhat  approaching  the 
true  resistance.  Unless  therefore  the  return  of  the  wing  gives 
a greater  degree  of  propelling  force  than  the  beat,  which  is  im- 
probable, no  such  resistance  of  the  body  could  be  sustained. 
Hence,  though  the  eye  cannot  perceive  any  distinction  between 
the  velocities  of  the  beat  and  return  of  the  wing,  it  probably 
exists,  and  experiment  alone  can  determine  the  proper  ratios 
between  them. 

From  these  observations  we  may,  however,  be  justified  in  the 
remark  — that  the  act  of  flying,  when  properly  adjusted  by  the 
Supreme  Author  of  every  power,  requires  less  exertions  than, 
from  the  appearance,  is  supposed. 


INTRODUCTION  TO  MR.  WENHAM’S  PAPER. 

The  following  paper,  “ On  Aerial  Locomotion  and  the  Laws  by  which 
Heavy  Bodies  impelled  through  Air  are  Sustained,”  was  read  by  F.  H. 
Wenham,  Esq.,  at  the  first  meeting  of  the  Aeronautical  Society  of  Great 
Britain,  held  on  the  27th  day  of  June,  1866.  His  Grace  the  Duke  of 
Argyll  in  the  Chair. 

Referring  to  this  paper,  Mr.  John  H.  Ledeboer  in  the  December, 
1 908,  issue  of  English  Aeronautics  writes  as  follows  : 

“ It  is  not  possible  to  give  even  a resume  of  this  momentous  paper 
in  the  short  space  at  my  disposal ; I would  only  most  strongly  urge 
every  student  of  aviation  to  read  it  for  himself,  and  to  re-read  it ; for 
almost  every  word  it  contains  holds  good  at  the  present  day,  and  might, 
with  great  advantage,  have  been  studied  by  the  majority  of  budding 
aviators  whose  failures  are  of  such  frequent  occurrence.” 

Francis  Herbert  Wenham  died  in  Folkestone,  Eng- 
land, August  ii,  1908,  at  the  age  of  eighty-four. 


(First  printed  in  The  Annual  Report  of  The  Aeronautical  Society  of 
Great  Britain,  1866.  Reprinted  in  the  Aeronautical  Annual,  1895.) 


WENHAM  ON  AERIAL  LOCOMOTION. 


The  resistance  against  a surface  of  a defined  area,  passing 
rapidly  through  yielding  media,  may  be  divided  into  two 
opposing  forces.  One  arising  from  the  cohesion  of  the  sepa- 
rated particles ; and  the  other  from  their  weight  and  inertia, 
which,  according  to  well-known  laws,  will  require  a constant 
power  to  set  them  in  motion. 

In  plastic  substances,  the  first  condition,  that  of  cohesion, 
will  give  rise  to  the  greatest  resistance.  In  water  this  has  ver)'- 
little  retarding  effect,  but  in  air,  from  its  extreme  fluidity,  the 
cohesive  force  becomes  inappreciable,  and  all  resistances  are 
caused  by  its  weight  alone ; therefore,  a weight,  suspended 
from  a plane  surface,  descending  perpendicularly  in  air,  is 
limited  in  its  rate  of  fall  by  the  weight  of  air  that  can  be  set 
in  motion  in  a given  time. 

If  a weight  of  150  lbs.  is  suspended  from  a surface  of  the 
same  number  of  square  feet,  the  uniform  descent  will  be  1,300 
feet  per  minute,  and  the  force  given  out  and  expended  on  the 
air,  at  this  rate  of  fall,  will  be  nearly  six  horse-power;  and, 
conversely,  this  same  speed  and  power  must  be  communicated 
to  the  surface  to  keep  the  weight  sustained  at  a fixed  altitude. 
As  the  surface  is  increased,  so  does  the  rate  of  descent  and  its 
accompanying  power,  expended  in  a given  time,  decrease.  It 
might,  therefore,  be  inferred  that,  with  a sufficient  extent  of 
surface  reproduced,  or  worked  up  to  a higher  altitude,  a man 
might  by  his  exertions  raise  himself  for  a time,  while  the  sur- 
face descends  at  a less  speed. 

(.176) 


WENIIAM  ON  AERIAL  LOCOMOTION. 


177 


A man,  in  raising  his  own  body,  can  perform  4,250  units  of 
work  — that  is,  this  number  of  pounds  raised  one  foot  high  per 
minute  — and  can  raise  his  own  weight  — say,  150  lbs.  — 
twenty-two  feet  per  minute.  But  at  this  speed  the  atmospheric 
resistance  is  so  small  that  120,000  square  feet  would  be  re- 
quired to  balance  his  exertions,  making  no  allowance  for 
weight  beyond  his  own  body. 

We  have  thus  reasons  for  the  failure  of  the  many  misdirected 
attempts  that  have,  from  time  to  time,  been  made  to  raise 
weights  perpendicularly  in  the  air  by  wings  or  descending 
surfaces.  Though  the  flight  of  a bird  is  maintained  by  a con- 
stant reaction  or  abutment  against  an  enormous  weight  of  air 
in  comparison  with  the  weight  of  its  own  body,  yet,  as  will  be 
subsequently  shown,  the  support  upon  that  weight  is  not  nec- 
essarily commanded  by  great  extent  of  wing-surface,  but  by 
the  direction  of  motion. 

One  of  the  first  birds  in  the  scale  of  flying  magnitude  is  the 
pelican.  It  is  seen  in  the  streams  and  estuaries  of  warm  cli- 
mates, fish  being  its  only  food.  On  the  Nile,  after  the  inunda- 
tion, it  arrives  in  flocks  of  many  hundreds  together,  having 
migrated  from  long  distances.  A specimen  shot  was  found 
to  weigh  twenty-one  pounds,  and  measured  ten  feet  across 
the  wings,  from  end  to  end.  The  pelican  rises  with  much 
difficulty,  but,  once  on  the  wing,  appears  to  fly  with  very  little 
exertion,  notwithstanding  its  great  weight.  Their  mode  of 
progress  is  peculiar  and  graceful.  They  fly  after  a leader, 
in  one  single  train.  As  he  rises  or  descends,  so  his  followers 
do  the  same  in  succession,  imitating  his  movements  precisely. 
At  a distance,  this  gives  them  the  appearance  of  a long  undu- 
lating ribbon,  glistening  under  the  cloudless  sun  of  an  oriental 
sky.  During  their  flight  they  make  about  seventy  strokes  per 
minute  with  their  wings.  This  uncouth-looking  bird  is  some- 
what whimsical  in  its  habits.  Groups  of  them  may  be  seen  far 
above  the  earth,  at  a distance  from  the  river-side,  soaring,  ap- 
parently for  their  own  pleasure.  With  outstretched  and  motion- 
less wings,  they  float  serenely,  high  in  the  atmosphere,  for  more 
than  an  hour  together,  traversing  the  same  locality  in  circling 


178 


THE  AERONAUTICAL  ANNUAL. 


movements.  With  head  thrown  back,  and  enormous  bills 
resting  on  their  breasts,  they  almost  seem  asleep.  A few  easy 
strokes  of  their  wings  each  minute,  as  their  momentum  or  ve- 
locity diminishes,  serves  to  keep  them  sustained  at  the  same 
level.  The  effort  required  is  obviously  slight,  and  not  confirm- 
atory of  the  excessive  amount  of  power  said  to  be  requisite 
for  maintaining  the  flight  of  a bird  of  this  weight  and  size.  The 
pelican  displays  no  symptom  of  being  endowed  with  great 
strength,  for  when  only  slightly  wounded  it  is  easily  captured, 
not  having  adequate  power  for  effective  resistance,  but  heavily 
flapping  the  huge  wings,  that  should,  as  some  imagine,  give  a 
stroke  equal  in  vigour  to  the  kick  of  a horse. 

During  a calm  evening,  flocks  of  spoonbills  take  their  flight 
directly  up  the  river’s  course ; as  if  linked  together  in  unison, 
and  moved  by  the  same  impulse,  they  alter  not  their  relative 
positions,  but  at  less  than  fifteen  inches  above  the  water’s  sur- 
face, they  speed  swiftly  by  with  ease  and  grace  inimitable,  a 
living  sheet  of  spotless  white.  Let  one  circumstance  be  re- 
marked, — though  they  have  fleeted  past  at  a rate  of  near  thirty 
miles  an  hour,  so  little  do  they  disturb  the  element  in  which 
they  move,  that  not  a ripple  of  the  placid  bosom  of  the  river, 
which  they  almost  touch,  has  marked  their  track.  How  won- 
derfully does  their  progress  contrast  with  that  of  creatures  who 
are  compelled  to  drag  their  slow  and  weary  way  against  the 
fluid  a thousandfold  more  dense,  flowing  in  strong  and  eddying 
current  beneath  them. 

Our  pennant  droops  listlessly,  the  wished-for  north  wind 
cometh  not.  According  to  custom  we  step  on  shore,  gun  in 
hand.  A flock  of  white  herons,  or  “ buffalo-birds,”  almost 
within  our  reach,  run  a short  distance  from  the  pathway  as  we 
approach  them.  Others  are  seen  perched  in  social  groups  upon 
the  backs  of  the  apathetic  and  mud-begrimed  animals  whose 
name  they  bear.  Beyond  the  ripening  dhourra  crops  which 
skirt  the  river-side,  the  land  is  covered  with  immense  numbers 
of  blue  pigeons,  flying  to  and  fro  in  shoals,  and  searching  for 
food  with  restless  diligence.  The  musical  whistle  from  the 
pinions  of  the  wood-doves  sounds  cheerily,  as  they  dart  past 


WENHAM  ON  AERIAL  LOCOMOTION. 


179 


with  the  speed  of  an  arrow.  Ever  and  anon  are  seen  a covey 
of  the  brilliant,  many-coloured  partridges  of  the  district,  whose 
long  and  pointed  wings  give  them  a strength  and  duration  of 
flight  that  seems  interminable,  alighting  at  distances  beyond  the 
possibility  of  marking  them  down,  as  we  are  accustomed  to  do 
with  their  plumper  brethren  at  home.  But  still  more  remark- 
able is  the  spectacle  which  the  sky  presents.  As  far  as  the  eye 
can  reach  it  is  dotted  with  birds  of  prey  of  every  size  and  de- 
scription. Eagles,  vultures,  kites  and  hawks,  of  manifold 
species,  down  to  the  small,  swallow-like,  insectivorous  hawk 
common  in  the  Delta,  which  skims  the  surface  of  the  ground  in 
pursuit  of  its  insect  prey.  None  seem  bent  on  going  forward, 
but  all  are  soaring  leisurely  round  over  the  same  locality,  as  if 
the  invisible  element  which  supports  them  were  their  medium 
of  rest  as  well  as  motion.  But  mark  that  object  sitting  in  soli- 
tary state  in  the  midst  of  yon  plain  : what  a magnificent  eagle  ! 
An  approach  to  within  eighty  yards  arouses  the  king  of  birds 
from  his  apathy.  He  partly  opens  his  enormous  wings,  but 
stirs  not  yet  from  his  station.  On  gaining  a few  feet  more  he 
begins  to  walk  away,  with  half-expanded,  but  motionless  wings. 
Now  for  the  chance  fire!  A charge  of  No.  3 from  ii  bore 
rattles  audibly  but  ineffectively  upon  his  densely  feathered 
body;  his  walk  increases  to  a run,  he  gathers  speed  with  his 
slowly-waving  wings,  and  eventually  leaves  the  ground.  Rising 
at  a gradual  inclination,  he  mounts  aloft  and  sails  majestically 
away  to  his  place  of  refuge  in  the  Lybian  range,  distant  at 
least  five  miles  from  where  he  rose.  Some  fragments  of  feathers 
denote  the  spot  where  the  shot  had  struck  him.  The  marks 
of  his  claws  are  traceable  in  the  sandy  soil,  as,  at  first  with  firm 
and  decided  digs,  he  forced  his  way,  but  as  he  lightened  his 
body  and  increased  his  speed  with  the  aid  of  his  wings,  the  im- 
prints of  his  talons  gradually  merged  into  long  scratches.  The 
measured  distance  from  the  point  where  these  vanished,  to  the 
place  where  he  had  stood,  proved  that  with  all  the  stimulus  that 
the  shot  must  have  given  to  his  exertions,  he  had  been  compelled 
to  run  full  twenty  yards  before  he  could  raise  himself  from  the 
earth. 


i8o 


THE  AERONAUTICAL  ANNUAL. 


Again  the  boat  is  under  weigh,  though  the  wind  is  but  just 
sufficient  to  enable  us  to  stem  the  current.  An  immense  kite 
is  soaring  overhead,  scarcely  higher  than  the  top  of  our  lateen 
yard,  affording  a fine  opportunity  for  contemplating  his  easy 
and  unlaboured  movements.  The  cook  has  now  thrown  over- 
board some  offal.  With  a solemn  swoop  the  bird  descends 
and  seizes  it  in  his  talons.  How  easily  he  rises  again  with 
motionless  expanded  wings,  the  mere  force  and  momentum  of 
his  desce^tt  serving  to  raise  him  again  to  more  than  half-mast 
high.  Observe  him  next,  with  lazy  flapping  wings,  and  head 
turned  under  his  body;  he  is  placidly  devouring  the  pendant 
morsel  from  his  foot,  and  calmly  gliding  onwards. 

The  Nile  abounds  with  large  aquatic  birds  of  almost  every 
variety.  During  a residence  upon  its  surface  for  nine  months 
out  of  the  year,  immense  numbers  have  been  seen  to  come  and 
go,  for  the  majority  of  them  are  migratory.  Egypt  being 
merely  a narrow  strip  of  territory,  passing  through  one  of  the 
most  desert  parts  of  the  earth,  and  rendered  fertile  only  by  the 
periodical  rise  of  the  waters  of  the  river,  it  is  probable  that 
these  birds  make  it  their  grand  thoroughfare  into  the  rich 
districts  of  Central  Africa. 

On  nearing  our  own  shores,  steaming  against  a moderate 
head-wind,  from  a station  abaft  the  wheel  the  movements  of 
some  half-dozen  gulls  are  observed,  following  in  the  wake  of 
the  ship,  in  patient  expectation  of  any  edibles  that  may  be 
thrown  overboard.  One  that  is  more  familiar  than  the  rest 
comes  so  near  at  times  that  the  winnowing  of  his  wings  can  be 
heard ; he  has  just  dropped  astern,  and  now  comes  on  again. 
With  the  axis  of  his  body  exactly  at  the  level  of  the  eyesight, 
his  every  movement  can  be  distinctly  marked.  He  approaches 
to  within  ten  yards,  and  utters  his  wild  plaintive  note,  as  he 
turns  his  head  from  side  to  side,  and  regards  us  with  his  jet 
black  eye.  But  where  is  the  angle  or  upward  rise  of  his  wings, 
that  should  compensate  for  his  descending  tendency,  in  a yield- 
ing medium  like  air?  The  incline  cannot  be  detected,  for,  to 
all  appearance,  his  wings  are  edgewise,  or  parallel  to  his  line  of 
motion,  and  he  appears  to  skim  along  a solid  support.  No 


CROVSR  C.  BERGDOU 

WENHAM  ON  AERIAL  LOCOMOTION.  l8l 

smooth-edged  rails,  or  steel-tired  wheels,  with  polished  axles 
revolving  in  well  oiled  brasses,  are  needed  here  for  the  purpose 
of  diminishing  friction,  for  Nature’s  machinery  has  surpassed 
them  all.  The  retarding  effects  of  gravity  in  the  creature  under 
notice,  are  almost  annulled,  for  he  is  gliding  forward  upon  a 
frictionless  plane.  There  are  various  reasons  for  concluding 
that  the  direct  flight  of  many  birds  is  maintained  with  a much 
less  expenditure  of  power,  for  a high  speed,  than  by  any  mode 
of  progression. 

The  first  subject  for  consideration  is  the  proportion  of  surface 
to  weight,  and  their  combined  effect  in  descending  perpendicu- 
larly through  the  atmosphere.  The  datum  is  here  based  upon 
the  consideration  of  safety,  for  it  may  sometimes  be  needful  for 
a living  being  to  drop  passively,  without  muscular  effort.  One 
square  foot  of  sustaining  surface,  for  every  pound  of  the  total 
weight,  will  be  sufficient  for  security. 

According  to  Smeaton’s  table  of  atmospheric  resistances,  to 
produce  a force  of  one  pound  on  a square  foot,  the  wind  must 
move  against  the  plane  (or,  which  is  the  same  thing,  the  plane 
against  the  wind),  at  the  rate  of  twenty-two  feet  per  second,  or 
1,320  feet  per  minute,  equal  to  fifteen  miles  per  hour.  The 
resistance  of  the  air  will  now  balance  the  weight  on  the  descend  - 
ing surface,  and,  consequently,  it  cannot  exceed  that  speed. 
Now,  twenty-two  feet  per  second  is  the  velocity  acquired  at  the 
end  of  a fall  of  eight  feet  — a height  from  which  a well-knit 
man  or  animal  may  leap  down  without  much  risk  of  injury. 
Therefore,  if  a man  with  parachute  weigh  together  143  lbs., 
spreading  the  same  number  of  square  feet  of  surface  contained 
in  a circle  fourteen  and  a half  feet  in  diameter,  he  will  descend 
at  perhaps  an  unpleasant  velocity,  but  with  safety  to  life  and 
limb. 

It  is  a remarkable  fact  how  this  proportion  of  wing-surface  to 
weight  extends  throughout  a great  variety  of  the  flying  portion 
of  the  animal  kingdom,  even  down  to  hornets,  bees,  and  other 
insects.  In  some  instances,  however,  as  in  the  gallinaceous 
tribe,  including  pheasants,  this  area  is  somewhat  exceeded,  but 
they  are  known  to  be  very  poor  flyers.  Residing  as  they  do 


i82 


THE  AERONAUTICAL  ANNUAL. 


chiefly  on  the  ground,  their  wings  are  only  required  for  short 
distances,  or  for  raising  them  or  easing  their  descent  from  their 
roosting-places  in  forest  trees,  the  shortness  of  their  wings  pre- 
venting them  from  taking  extended  flights.  The  wing-surface 
of  the  common  swallow  is  rather  more  than  in  the  ratio  of  two 
square  feet  per  pound,  but  having  also  great  length  of  pinion,  it 
is  both  swift  and  enduring  in  its  flight.  When  on  a rapid  course 
this  bird  is  in  the  habit  of  furling  its  wings  into  a narrow  com- 
pass. The  greater  extent  of  surface  is  probably  needful  for 
the  continual  variations  of  speed  and  instant  stoppages  requisite 
for  obtaining  its  insect  food. 

On  the  other  hand,  there  are  some  birds,  particularly  of  the 
duck  tribe,  whose  wing-surface  but  little  exceeds  half  a square 
foot,  or  seventy-two  inches  per  pound,  yet  they  may  be  classed 
among  the  strongest  and  swiftest  of  flyers.  A weight  of  one 
pound,  suspended  from  an  area  of  this  extent,  would  acquire  a 
velocity  due  to  a fall  of  l6  feet  — a height  sufficient  for  the 
destruction  or  injury  of  most  animals.  But  when  the  plane  is 
urged  forward  horizontally,  in  a manner  analogous  to  the  wings 
of  a bird  during  flight,  the  sustaining  power  is  greatly  influenced 
by  the  foriti  and  arrangement  of  the  surface. 

In  the  case  of  perpe7idicular  descent,  as  a parachute,  the  sus- 
taining effect  will  be  much  the  same,  whatever  the  figure  of  the 
outline  of  the  superficies  may  be,  and  a circle  perhaps  affords 
the  best  resistance  of  any.  Take  for  example  a circle  of  20 
square  feet  (as  possessed  by  the  pelican)  loaded  with, as  many 
pounds.  This,  as  just  stated,  will  limit  the  rate  of  perpendicular 
descent  to  1,320  feet  per  minute.  But  instead  of  a circle  61 
inches  in  diameter,  if  the  area  is  bounded  by  a parallelogram 
10  feet  long  by  2 feet  broad,  and  whilst  at  perfect  freedom  to 
descend  perpendicularly,  let  a force  be  applied  exactly  in  a 
horizontal  direction,  so  as  to  carry  it  edgeways,  with  the  long 
side  foremost,  at  a forward  speed  of  30  miles  per  hour — just 
double  that  of  its  passive  descent:  the  rate  of  fall  under  these 
conditions  will  be  decreased  most  remarkably,  probably  to  less 
than  i\th  part,  or  88  feet  per  minute,  or  one  mile  per  hour. 

The  annexed  line  represents  transversely  the  plane  2 feet 


WENHAM  ON  AERIAL  LOCOMOTION. 


183 


wide  and  10  feet  long,  moving  in  the  direction  of  the  arrow 


with  a forward  speed  of  30  miles  per  hour,  or  2,640  feet  per 
minute,  and  descending  at  88  feet  per  minute,  the  ratio 
being  as  i to  30.  Now,  the  particles  of  air,  caught  by  the 
forward  edge  of  the  plane,  must  be  carried  down  -/oths  of  an 
inch  before  they  leave  it.  This  stratum,  10  feet  wide  and 
2,640  long,  will  weigh  not  less  than  134  lbs.;  therefore  the 
weight  has  continually  to  be  moved  downwards,  88  feet  per 
minute,  from  a state  of  absolute  rest.  If  the  plane,  with  this 
weight  and  an  upward  rise  of  y%ths  of  an  inch,  be  carried  forward 
at  a rate  of  30  miles  per  hour,  it  will  be  maintained  at  the  same 
level  without  descending. 

The  following  illustrations,  though  referring  to  the  action  of 
surfaces  in  a denser  fluid,  are  yet  exactly  analogous  to  the  con- 
ditions set  forth  in  air : — 

Take  a stiff  rod  of  wood,  and  nail  to  its  end  at  right  angles  a 
thin  lath  or  blade,  about  two  inches  wide.  Place  the  rod  square 
across  the  thwarts  of  a rowing-boat  in  motion,  letting  a foot 
or  more  of  the  blade  hang  perpendicularly  over  the  side  into 
the  water.  The  direct  amount  of  resistance  of  the  current 
against  the  flat  side  of  the  blade  may  thus  be  felt.  Next  slide 
the  rod  to  and  fro  thwart  ship,  keeping  all  square ; the  resistance 
will  now  be  found  to  have  increased  enormously ; indeed,  the 
boat  can  be  entirely  stopped  by  such  an  appliance.  Of  course 
the  same  experiment  may  be  tried  in  a running  stream. 

Another  familiar  example  may  be  cited  in  the  lee-boards  and 
sliding  keels  used  in  vessels  of  shadow  draught,  which  act  pre- 
cisely on  the  same  principle  as  the platie  or  wing-siirface  of  a bird 
when  moving  in  air.  These  surfaces,  though  parallel  to  the  line 
of  the  vessel’s  course,  enable  her  to  carry  a heavy  press  of  sail 
without  giving  way  under  the  side  pressure,  or  making  lee-way, 
so  great  is  their  resistance  against  the  rapidly  passing  body  of 
water,  which  cannot  be  deflected  sideways  at  a high  speed. 

The  succeeding  experiments  will  serve  further  to  exemplify 


THE  AERONAUTICAL  ANNUAL. 


184 

the  action  of  the  same  principle.  Fix  a thin  blade,  say  one 
inch  wide  and  one  foot  long,  with  its  plane  exactly  midway  and 
at  right  angles,  to  the  end  of  a spindle  or  rod.  On  thrusting 
this  through  a body  of  water,  or  immersing  it  in  a stream  run- 
ning in  the  direction  of  the  axis  of  the  spindle,  the  resistance 
will  be  simply  that  caused  by  the  water  against  the  mere  super- 
ficies of  the  blade.  Next  put  the  spindle  and  blade  in  rapid 
rotation.  The  retarding  effect  against  direct  motion  will  now  be 
increased  near  tenfold,  and  is  equal  to  that  due  to  the  entire  area 
of  the  circle  of  revolution.  By  trying  the  effect  of  blades  of 
various  widths,  it  will  be  found  that,  for  the  purpose  of  effect- 
ing the  maximum  amount  of  resistance,  the  more  rapidly  the 
spindle  revolves  the  narrower  may  be  the  blade.  There  is  a 
specific  ratio  between  the  width  of  the  blade  and  its  velocity. 
It  is  of  some  importance  that  this  should  be  precisely  defined, 
not  only  for  its  practical  utility  in  determining  the  best  propor- 
tion of  width  to  speed  in  the  blades  of  screw-propellers,  but 
also  for  a correct  demonstration  of  the  principles  involved  in 
the  subject  now  under  consideration:  for  it  maybe  remarked 
that  the  swiftest-flying  birds  possess  extremely  long  and  narrow 
wings,  and  the  slow,  heavy  flyers  short  and  wide  ones. 

In  the  early  days  of  the  screw-propeller,  it  was  thought 
requisite,  in  order  to  obtain  the  advantage  of  the  utmost  extent 
of  surface,  that  the  end-view  of  the  screw  should  present  no 
opening,  but  appear  as  a complete  disc.  Accordingly,  some 
were  constructed  with  one  or  two  threads,  making  an  entire  or  two 
half-revolutions ; but  this  was  subsequently  found  to  be  a mis- 
take. In  the  case  of  the  two  blades,  the  length  of  the  screw 
was  shortened,  and  consequently  the  width  of  the  blades  re- 
duced, with  increased  effect,  till  each  was  brought  down  to 
considerably  less  than  one-sixth  of  the  circumference  or  area 
of  the  entire  circle ; the  maximum  speed  was  then  obtained. 
Experiment  has  also  shown  that  the  effective  propelling  area  of 
the  two-bladed  screw  is  tantamount  to  its  entire  circle  of  revolu- 
tion, and  is  generally  estimated  as  such. 

Many  experiments  tried  by  the  author,  with  various  forms  of 
screws,  applied  to  a small  steam-boat,  led  to  the  same  conclu- 


WENHAM  ON  AERIAL  LOCOMOTION.  1 85 

sion  — that  the  two  blades  of  one-sixth  of  the  circle  gave  the 
best  result. 

All  screws  reacting  on  a fluid  such  as  water,  must  cause  it  to 
yield  to  some  extent;  this  is  technically  known  as  “ slip,”  and 
whatever  the  ratio  or  per-centage  on  the  speed  of  the  boat  may 
be,  it  is  tantamount  to  just  so  much  loss  of  propelling  power — 
this  being  consumed  in  giving  motion  to  the  water  instead  of 
the  boat. 

On  starting  the  engine  of  the  steam-boat  referred  to,  and 
grasping  a mooring-rope  at  the  stern,  it  was  an  easy  matter  to 
hold  it  back  with  one  hand,  though  the  engine  was  equal  in 
power  to  five  horses,  and  the  screw  making  more  than  500 
revolutions  per  minute.  The  whole  force  of  the  steam  was 
absorbed  in  “slip,”  or  in  giving  motion  to  the  column  of  water; 
but  let  her  go,  and  allow  the  screw  to  find  an  abutment  on  a 
fresh  body  of  water,  not  having  received  a gradual  motion,  and 
with  its  mertia  undisturbed  when  running  under  full  way,  the 
screw  worked  almost  as  if  in  a solid  nut,  the  “slip  ” amounting 
to  only  eleven  per  cent. 

The  laws  which  control  the  action  of  inclined  surfaces,  mov- 
ing either  in  straight  lines  or  circles  in  air,  are  identical,  and 
serve  to  show  the  inutility  of  attempting  to  raise  a heavy  body 
in  the  atmosphere  by  means  of  rotating  vanes  or  a screw  acting 
vertically ; for  unless  the  ratio  of  surface  compared  to  weight  is 
exceedingly  extensive,  the  whole  power  will  be  consumed  in 
“ slip,”  or  in  giving  a downward  motion  to  the  column  of  air. 
Even  if  a sufficient  force  is  obtained  to  keep  a body  suspended 
by  such  means,  yet,  after  the  desired  altitude  is  arrived  at,  no 
further  ascension  is  required  ; there  the  apparatus  is  to  remain 
stationary  as  to  level,  and  its  position  on  the  constantly  yielding 
support  can  only  be  maintained  at  an  enormous  expenditure  of 
power,  for  the  screw  cannot  obtain  a hold  upon  a fresh  and 
tmmoved  portion  of  air  in  the  same  manner  as  it  does  upon  the 
body  of  water  when  propelling  the  boat  at  full  speed  ; its  action 
under  these  conditions  is  the  same  as  when  the  boat  is  held 
fast,  in  which  case,  although  the  engine  is  working  up  to  its 
usual  rate,  the  tractive  power  is  almost  annulled. 


1 86  the  aeronautical  annual. 

Some  experiments  made  with  a screw,  or  pair  of  inclined 
vanes  acting  vertically  in  air,  were  tried,  in  the  following 
manner.  To  an  upright  post  was  fixed  a frame,  containing  a 
bevil  wheel  and  pinion,  multiplying  in  the  ratio  of  three  to  one. 
The  axle  of  the  wheel  was  horizontal,  and  turned  by  a handle 
of  five-and-a-half  inches  radius.  The  spindle  of  the  pinion 
rotated  vertically,  and  carried  two  driving-pins  at  the  end  of  a 
cross-piece,  so  that  the  top  resembled  the  three  prongs  of 
a trident.  The  upright  shaft  of  the  screw  was  bored  hollow  to 
receive  the  middle  prong,  while  the  two  outside  ones  took  a 
bearing  against  a driving-bar,  at  right  angles  to  the  lower  end 
of  the  shaft,  the  top  of  which  ended  in  a long  iron  pivot,  run- 
ning in  a socket  fixed  in  a beam  overhead ; it  could  thus  rise 
and  fall  about  two  inches  with  very  little  friction.  The  top  of 
the  screw-shaft  carried  a cross-arm,  with  a blade  of  equal  size 
at  each  extremity,  the  distance  from  end  to  end  being  six  feet. 
The  blades  could  be  adjusted  at  any  angle  by  clamping-screws. 
Both  their  edges,  and  the  arms  that  carried  them,  were  bevilled 
away  to  a sharp  edge  to  diminish  the  effects  of  atmospheric 
resistance.  A wire  stay  was  taken  from  the  base  of  each  blade 
to  the  bottom  of  the  upright  shaft,  to  give  rigidity  to  the  arms, 
and  to  prevent  them  from  springing  upwards.  With  this 
apparatus  experiments  were  made  with  weights  attached  to  the 
upright  screw-shaft,  and  the  blades  set  at  different  pitches,  or 
angles  of  inclination.  When  the  vanes  were  rotated  rapidly, 
they  rose  and  floated  on  the  air,  carrying  the  weights  with 
them.  Much  difficulty  was  experienced  in  raising  a heavy 
weight  by  a comparatively  small  extent  of  surface,  moving  at  a 
high  velocity ; the  “slip”  in  these  cases  being  so  great  as  to 
absorb  all  the  power  employed.  The  utmost  effect  obtained  in 
this  way  was  to  raise  a weight  of  six  pounds  on  one  square 
foot  of  sustaining  surface,  the  planes  having  been  set  at  a coarse 
pitch.  To  keep  up  the  rotation,  required  about  half  the  power 
a man  could  exert. 

The  ratio  of  weight  to  sustaining  surface  was  next  arranged 
in  the  proportion  approximating  to  that  of  birds.  Two  of  the 
experiments  are  here  quoted,  which  gave  the  most  satisfactory 


WENHAM  ON  AERIAL  LOCOMOTION. 


187 


result.  Weight  of  wings  and  shaft,  17^  oz. ; area  of  two  wings, 
121  inches  — equal  to  no  square  inches  per  pound.  The 
annexed  figures  are  given  approximately,  in  order  to  avoid 
decimal  fractions : — 


No.  of 
revolu- 
tions per 
minute. 

Mean 
sustain- 
ing speed. 
Miles  per 
hour. 

Feet 

per 

minute. 

Pitch  or 
angfle  of 
rise  in  one 
revolu- 
tion. 
Inches. 

Ratio  of 
pitch  to 
speed. 

Slip 

per 

cent. 

1st  Experiment 

210 

38 

3.360 

26 

J th  nearly 

12^ 

2nd  Do. 

240 

44 

3.S40 

15 

■j^th  Do. 

8 

The  power  required  to  drive  was  nearly  the  same  in  both 
experiments  — about  equal  to  one-sixteenth  part  of  a horse- 
power, or  the  third  part  of  the  strength  of  a man,  as  estimated 
by  a constant  force  on  the  handle  of  twelve  pounds  in  the  first 
experiment,  and  ten  in  the  second,  the  radius  of  the  handle 
being  five-and-a-half  inches,  and  making  seventy  revolutions 
per  minute  in  the  first  case,  and  eighty  in  the  other. 

These  experiments  are  so  far  satisfactory  in  showing  the 
small  pitch  or  angle  of  rise  required  for  sustaining  the  weight 
stated,  and  demonstrating  the  principle  before  alluded  to,  of  the 
slow  descent  of  planes  moving  horizontally  in  the  atmosphere 
at  high  velocities ; but  the  question  remains  to  be  answered, 
concerning  the  disposal  of  the  excessive  power  consumed  in 
raising  a weight  not  exceeding  that  of  a carrier  pigeon,  for 
unless  this  can  be  satisfactorily  accounted  for,  there  is  but  little 
prospect  of  finding  an  available  power,  of  sufficient  energy  in 
its  application  to  the  mechanism,  for  raising  apparatus,  either 
experimental  or  otherwise,  in  the  atmosphere.  In  the  second 
experiment,  the  screw-shaft  made  240  revolutions,  consequently, 
one  vane  (there  being  two)  was  constantly  passing  over  the 
same  spot  480  times  each  minute,  or  eight  times  in  a second. 
This  caused  a descending  current  of  air,  moving  at  the  rate  of 
near  four  miles  per  hour,  almost  sufficient  to  blow  a candle  out 
placed  three  feet  underneath.  This  is  the  result  of  “ slip,”  and 


i88 


THE  AERONAUTICAL  ANNUAL. 


the  giving  both  a downward  and  rotary  motion  to  this  column 
of  air,  will  account  for  a great  part  of  the  power  employed,  as 
the  whole  apparatus  performed  the  work  of  a blower.  If  the 
wings,  instead  of  travelling  in  a circle,  could  have  been  urged 
continually  forward  in  a straight  line  in  a fresh  and  unmoved 
body  of  air  the  “ slip  ” would  have  been  so  inconsiderable,  and 
the  pitch  consequently,  reduced  to  such  a small  angle,  as  to 
add  but  little  to  the  direct  forward  atmospheric  resistance  of 
the  edge. 

The  small  flying  screws,  sold  as  toys,  are  well  known.  It  is 
an  easy  matter  to  determine  approximately  the  force  expended 
in  raising  and  maintaining  them  in  the  atmosphere.  The  fol- 
lowing is  an  example  of  one  constructed  of  tin-plate  with  three 
equidistant  vanes.  This  was  spun  by  means  of  a cord,  wound 
round  a wooden  spindle,  fitted  into  a forked  handle  as  usual. 
The  outer  end  of  the  coiled  string  was  attached  to  a small 
spring  steelyard,  which  served  as  a handle  to  pull  it  out  by.  The 
weight,  or  degree  at  which  the  index  had  been  drawn,  was  after- 
wards ascertained  by  the  mark  left  thereon  by  a pointed  brass 
wire.  It  is  not  necessary  to  know  the  time  occupied  in  draw- 
ing out  the  string,  as  this  item  in  the  estimate  may  be  taken  as 
the  duration  of  the  ascent;  for  it  is  evident  that  if  the  same 
force  is  re-applied  at  the  descent,  it  would  rise  again,  and  a 
repeated  series  of  these  impulses  will  represent  the  power  re- 
quired to  prolong  the  flight  of  the  instrument.  It  is,  therefore, 
requisite  to  know  the  length  of  string,  and  the  force  applied  in 
pulling  it  out.  The  following  are  the  data : — 

Diameter  of  screw  ......  inches. 

Weight  of  ditto  .......  396  grains. 

Length  of  string  drawn  out  .....  2 feet. 

Force  employed  .......  8 lbs. 

Duration  of  flight  , . . . . .16  seconds. 

From  this  it  may  be  computed  that,  in  order  to  maintain  the 
flight  of  the  instrument,  a constant  force  is  required  of  near 
sixty  foot-pounds  per  minute  — in  the  ratio  of  about  three 


WENHAM  ON  AERIAL  LOCOMOTION.  1 89 

horse-power  for  each  hundred  pounds  raised  by  such  means. 
The  force  is  perhaps  over-estimated  for  a larger  screw,  for 
as  the  size  and  weight  is  increased,  the  power  required  would 
be  less  than  in  this  ratio.  The  result  would  be  more  satis- 
factory if  tried  with  a sheet-iron  screw,  impelled  by  a descend- 
ing weight. 

Methods  analogous  to  this  have  been  proposed  for  at- 
tempting aerial  locomotion ; but  experiment  has  shown  that 
a screw  rotating  in  the  air  is  an  imperfect  principle  for 
obtaining  the  means  of  flight,  and  supporting  the  needful 
weight,  for  the  power  required  is  enormous.  Suppose  a 
machine  to  be  constructed,  having  some  adequate  supply  of 
force,  the  screw  rotating  vertically  at  a certain  velocity  will 
raise  the  whole.  When  the  desired  altitude  is  obtained, 
nearly  the  same  velocity  of  revolution,  and  the  same  excessive 
power,  must  be  continued,  and  consumed  entirely  m “ slip!' 
or  in  drawing  down  a rapid  current  of  air. 

If  the  axis  of  the  screw  is  slightly  inclined  from  the  per- 
pendicular, the  whole  machine  will  travel  forward.  The 
“ slip,”  and  consequently  the  power,  is  somewhat  reduced  under 
these  conditions ; but  a swift  forward  speed  cannot  be  effected 
by  such  means,  for  the  resistance  of  the  inclined  disc  of  the 
screw  will  be  very  great,  far  exceeding  any  form  assimilating 
to  the  edge  of  the  wing  of  a bird.  But,  arguing  on  the 
supposition  that  a forward  speed  of  thirty  miles  an  hour 
might  thus  be  obtained,  even  then  nearly  all  the  power 
would  be  expended  in  giving  an  unnecessary  and  rapid  revo- 
lution to  an  immense  screw,  capable  of  raising  a weight,  say 
of  200  pounds.  The  weight  alone  of  such  a machine  must 
cause  it  to  fail,  and  every  revolution  of  the  screw  is  a sub- 
traction from  the  much-desired  direct  forward  speed.  A 
simple  narrow  blade,  or  inclined  plane,  propelled  in  a direct 
course  at  this  speed  — which  is  amply  sufficient  for  sustaining 
heavy  weights  — is  the  best,  and,  in  fact,  the  only  means  of 
giving  the  maximum  amount  of  supporting  power  with  the 
least  possible  degree  of  “ slip,”  and  direct  forward  resistance. 
Thousands  of  examples  in  Nature  testify  its  success,  and  show 


190 


THE  AERONAUTICAL  ANNUAL. 


the  principle  in  perfection ; — apparently  the  only  one,  and 
therefore  beyond  the  reach  of  amendment,  the  wing  of  a 
bird,  combining  a propelling  and  supporting  organ  in  one, 
each  perfectly  efficient  in  its  mechanical  action. 

This  leads  to  the  consideration  of  the  amount  of  power 
requisite  to  maintain  the  flight  of  a bird.  Anatomists  state 
that  the  pectoral  muscles  for  giving  motion  to  the  wings  are 
excessively  large  and  strong ; but  this  furnishes  no  proof  of  the 
expenditure  of  a great  amount  of  force  in  the  act  of  flying. 
The  wings  are  hinged  to  the  body  like  two  powerful  levers, 
and  some  counteracting  force  of  a passive  nature,  acting  like  a 
spring  under  tension,  must  be  requisite  merely  to  balance  the 
weight  of  the  bird.  It  cannot  be  shown  that,  while  there  is 
no  active  motion,  there  is  any  real  exertion  of  muscular 
force ; for  instance,  during  the  time  when  a bird  is  soaring 
with  motionless  wings.  This  must  be  considered  as  a state 
of  equilibrium,  the  downward  spring  and  elasticity  of  the 
wings  serving  to  support  the  body;  the  muscles,  in  such  a 
case,  performing  like  stretched  india-rubber  springs  would  do. 
The  motion  or  active  power  required  for  the  performance  of 
flight  must  be  considered  exclusive  of  this. 

It  is  difficult,  if  not  impossible,  by  any  form  of  dynamometer, 
to  ascertain  the  precise  amount  of  force  given  out  by  the  wings 
of  birds;  but  this  is  perhaps  not  requisite  in  proof  of  the  prin- 
ciple involved,  for  when  the  laws  governing  their  movements  in 
air  are  better  understood,  it  is  quite  possible  to  demonstrate, 
by  isolated  experiments,  the  amount  of  power  required  to  sus- 
tain and  propel  a given  weight  and  surface  at  any  speed. 

If  the  pelican  referred  to  as  weighing  twenty- one  pounds, 
with  near  the  same  amount  of  wing-area  in  square  feet,  were  to 
descend  perpendicularly,  it  would  fall  at  the  rate  of  1,320  feet 
per  minute,  being  limited  to  this  speed  by  the  resistance  of  the 
atmosphere. 

The  standard  generally  employed  in  estimating  power  is  by 
the  rate  of  descent  of  a weight.  Therefore,  the  weight  of  the 
bird  being  21  pounds,  which,  falling  at  the  above  speed  will 
expend  a force  on  the  air  set  in  motion  nearly  equal  to  one 


WENHAM  ON  AERIAL  LOCOMOTION.  19I 

horse  (.84  HP.)  or  that  of  5 men;  and  conversely,  to  raise  this 
weight  again  perpendicularly  upon  a yielding  support  like  air, 
would  require  even  more  power  than  this  expression,  which  it 
is  certain  that  a pelican  does  not  possess ; nor  does  it  appear 
that  any  large  bird  has  the  faculty  of  raising  itself  on  the  wing 
perpendictdarly  in  a still  atmosphere.  A pigeon  is  able  to 
accomplish  this  nearly,  mounting  to  the  top  of  a house  in  a 
very  narrow  compass ; but  the  exertion  is  evidently  severe,  and 
can  only  be  maintained  for  a short  period.  For  its  size,  this 
bird  has  great  power  of  wing ; but  this  is  perhaps  far  exceeded 
in  the  humming-bird,  which,  by  the  extremely  rapid  movements 
of  its  pinions,  sustains  itself  for  more  than  a minute  in  still  air 
in  one  position.  The  muscular  force  required  for  this  feat  is 
much  greater  than  for  any  other  performance  of  flight.  The  body 
of  the  bird  at  the  time  is  nearly  vertical.  The  wings  uphold  the 
weight,  not  by  striking  vertically  downwards  upon  the  air, 
but  as  inclined  surfaces  reciprocating  horizontally  like  a screw, 
but  wanting  in  its  continuous  rotation  in  one  direction,  and,  in 
consequence  of  the  loss  arising  from  rapid  alternations  of  motion, 
the  power  required  for  the  flight  will  exceed  that  specified  in 
the  screw  experiment  before  quoted,  viz. ; three  horse-power 
for  every  100  pounds  raised. 

We  have  here  an  example  of  the  exertion  of  enormous 
animal  force  expended  in  flight,  necessary  for  the  peculiar 
habits  of  the  bird,  and  for  obtaining  its  food ; but  in  the  other 
extreme,  in  large  heavy  birds,  whose  wings  are  merely  required 
for  the  purposes  of  migration  or  locomotion,  flight  is  obtained 
with  the  least  possible  degree  of  power,  and  this  condition  can 
only  be  commanded  by  a rapid  straightforward  course  through 
the  air. 

The  sustaining  power  obtained  in  flight  must  depend  upon 
certain  laws  of  action  and  reaction  between  relative  weights ; 
the  weight  of  a bird,  balanced,  or  finding  an  abutment,  against 
the  fixed  inertia  of  a far  greater  weight  of  air,  continuously 
brought  into  action  in  a given  time.  This  condition  is  secured, 
not  by  extensive  surface,  but  by  great  length  of  wing,  which, 
in  forward  motion,  takes  a support  upon  a wide  stratum  of  air, 
extending  transversely  to  the  line  of  direction. 


192 


THE  AERONAUTICAL  ANNUAL. 


The  pelican,  for  example,  has  wings  extending  out  lo  feet. 
If  the  limits  of  motion  imparted  to  the  substratum  of  air,  acted 
upon  by  the  incline  of  the  wing,  be  assumed  as  one  foot  in 
thickness,  and  the  velocity  of  flight  as  30  miles  per  hour,  or 
2,640  feet  per  minute,  the  stratum  of  air  passed  over  in  this 
time  will  weigh  nearly  one  ton,  or  100  times  the  weight  of  the 
body  of  the  bird,  thus  giving  such  an  enormous  supporting 
power,  that  the  comparatively  small  weight  of  the  bird  has  but 
little  effect  in  deflecting  the  heavy  length  of  stratum  downwards, 
and,  therefore,  the  higher  the  velocity  of  flight  the  less  the 
amount  of  “ slip,”  or  power  wasted  in  compensation  for  descent. 

As  noticed  at  the  commencement  of  this  paper,  large  birds 
may  be  observed  to  skim  close  above  smooth  water  without 
ruffling  the  surface ; showing  that  during  rapid  flight  the  air 
does  not  give  way  beneath  them,  but  approximates  towards  a 
solid  support. 

In  all  inclined  surfaces,  moving  rapidly  through  air,  the 
whole  sustaining  power  approaches  toward  the  front  edge ; and 
in  order  to  exemplify  the  inutility  of  surface  alone,  without  pro- 
portionate length  of  wing,  take  a plane,  ten  feet  long  by  two 
broad,  impelled  with  the  narrow  end  forward,  the  first  twelve  or 
fifteen  inches  will  be  as  efficient  at  a high  speed  in  supporting 
a weight  as  the  entire  following  portion  of  the  plane,  which 
may  be  cut  off,  thus  reducing  the  effective  wing-area  of  a peli- 
can, arranged  in  this  direction,  to  the  totally  inadequate  equiva- 
lent of  two-and-a-half  square  feet. 

One  of  the  most  perfect  natural  examples  of  easy  and  long- 
sustained  flight  is  the  wandering  albatross.  “ A bird  for 
endurance  of  flight  probably  unrivalled.  Found  over  all  parts 
of  the  Southern  Ocean,  it  seldom  rests  on  the  water.  During 
storms,  even  the  most  terrific,  it  is  seen  now  dashing  through 
the  whirling  clouds,  and  now  serenely  floating,  without  the  least 
observable  motion  of  its  outstretched  pinions.”  The  wings  of 
this  bird  extend  fourteen  or  fifteen  feet  from  end  to  end,  and 
measure  only  eight-and-a-half  inches  across  the  broadest  part. 
This  conformation  gives  the  bird  such  an  extraordinary  sustain- 
ing power,  that  it  is  said  to  sleep  on  the  wing  during  stormy 


WENHAM  ON  AERIAL  LOCOMOTION. 


193 


weather,  when  rest  on  the  ocean  is  impossible.  Rising  high  in 
the  air,  it  skims  slowly  down,  with  absolutely  motionless  wings, 
till  a near  approach  to  the  waves  awakens  it,  when  it  rises  again 
for  another  rest. 

If  the  force  expended  in  actually  sustaining  a long-winged 
bird  upon  a wide  and  unyielding  stratum  of  air,  during  rapid 
flight,  is  but  a small  fraction  of  its  strength,  then  nearly  the 
whole  is  exerted  in  overcoming  direct  forward  resistance.  In 
the  pelican  referred  to,  the  area  of  the  body,  at  its  greatest 
diameter,  is  about  100  square  inches;  that  of  the  pinions, 
eighty.  But  as  the  contour  of  many  birds  during  flight  ap- 
proximates nearly  to  Newton’s  solid  of  least  resistance,  by 
reason  of  this  form,  acting  like  the  sharp  bows  of  a ship,  the 
opposing  force  against  the  wind  must  be  reduced  down  to  one 
third  or  fourth  part ; this  gives  one-tenth  of  a horse-power,  or 
about  half  the  strength  of  a man,  expended  during  a flight  of 
thirty  miles  per  hour.  Judging  from  the  action  of  the  living 
bird  when  captured,  it  does  not  appear  to  be  more  powerful 
than  here  stated. 

The  transverse  area  of  a carrier  pigeon  during  flight  (includ- 
ing the  outstretched  wings)  a little  exceeds  the  ratio  of  twelve 
square  inches  for  each  pound,  and  the  wing-surface,  or  sustain- 
ing area,  ninety  square  inches  per  pound. 

Experiments  have  been  made  to  test  the  resisting  power  of 
conical  bodies  of  various  forms,  in  the  following  manner : — A 
thin  lath  was  placed  horizontally,  so  as  to  move  freely  on  a 
pivot  set  midway ; at  one  end  of  the  lath  a circular  card  was 
attached,  at  the  other  end  a sliding  clip  traversed,  for  holding 
paper  cones,  having  their  bases  the  exact  size  of  the  opposite 
disc.  The  instrument  acted  like  a steelyard ; and  when  held 
against  the  wind,  the  paper  cones  were  adjusted  at  different 
distances  from  the  centre,  according  to  their  forms  and  angles, 
in  order  to  balance  the  resistance  of  the  air  against  the  oppos- 
ing flat  surface.  The  resistance  was  found  to  be  diminished 
nearly  in  the  ratio  that  the  height  of  the  cone  exceeded  the 
diameter  of  base. 

It  might  be  expected  that  the  pull  of  the  string  of  a flying  kite 


194 


THE  AERONAUTICAL  ANNUAL. 


should  give  some  indication  of  the  force  of  inclined  surfaces 
acting  against  a current  of  air;  but  no  correct  data  can  be 
obtained  in  this  way.  The  incline  of  the  kite  is  far  greater  than 
ever  appears  in  the  case  of  the  advancing  wing-surface  of  a bird. 
The  tail  is  purposely  made  to  give  steadiness  by  a strong  pull 
backwards  from  the  action  of  the  wind,  which  also  exerts  con- 
siderable force  on  the  suspended  cord,  which  for  more  than 
half  its  length  hangs  nearly  perpendicularly.  But  the  kite,  as 
a means  of  obtaining  unlimited  lifting  and  tractive  power,  in 
certain  cases  where  it  might  be  usefully  applied,  seems  to  have 
been  somewhat  neglected.  For  its  power  of  raising  weights, 
the  following  quotation  is  taken  from  Vol.  XLI.  of  the  Transac- 
tions of  the  Society  of  Arts,  relating  to  Captain  Dansey’s  mode 
of  communicating  with  a lee-shore.  The  kite  was  made  of  a 
sheet  of  holland  exactly  nine  feet  square,  extended  by  two  spars 
placed  diagonally,  and  as  stretched  spread  a surface  of  fifty-five 
square  feet,  “The  kite,  in  a strong  breeze,  extended  i,ioo 
yards  of  line  five-eighths  in  circumference,  and  would  have 
extended  more  had  it  been  at  hand.  It  also  extended  360 
yards  of  line,  one  and  three-quarters  of  an  inch  in  circum- 
ference, weighing  sixty  pounds.  The  holland  weighed  three 
and  a half  pounds ; the  spars,  one  of  which  was  armed  at  the 
head  with  iron  spikes,  for  the  purpose  of  mooring  it,  six  and 
three-quarter  pounds;  and  the  tail  was  five  times  its  length, 
composed  of  eight  pounds  of  rope  and  fourteen  of  elm  plank, 
weighing  together  twenty-two  pounds,” 

We  have  here  the  remarkable  fact  of  ninety- two  and  a quarter 
pounds  carried  by  a surface  of  only  fifty-five  square  feet. 

As  all  such  experiments  bear  a very  close  relation  to  the  sub- 
ject of  this  paper,  it  may  be  suggested  that  a form  of  kite 
should  be  employed  for  reconnoitring  and  exploring  purposes, 
in  lieu  of  balloons  held  by  ropes.  These  would  be  torn  to 
pieces  in  the  very  breeze  that  would  render  a kite  most  service- 
able and  safe.  In  the  arrangement  there  should  be  a smaller 
and  upper'kite,  capable  of  sustaining  the  weight  of  the  appara- 
tus. The  lower  kite  should  be  as  nearly  as  practicable  in  the 
form  of  a circular  flat  plane,  distended  with  ribs,  with  a car 


GROVIR  C.  BERGDOLL 


WENHAM  ON  AERIAL  LOCOMOTION.  195 

attached  beneath  like  a parachute.  Four  guy-ropes  leading  to 
the  car  would  be  required  for  altering  the  angle  of  the  plane  — 
vertically  with  respect  to  the  horizon,  and  laterally  relative  to 
the  direction  of  the  wind.  By  these  means  the  observer  could 
regulate  his  altitude,  so  as  to  command  a view  of  a country,  in 
a radius  of  at  least  twenty  miles ; he  could  veer  to  a great 
extent  from  side  to  side,  from  the  wind’s  course,  or  lower  him- 
self gently,  with  the  choice  of  a suitable  spot  for  descent. 
Should  the  cord  break,  or  the  wind  fail,  the  kite  would,  in  either 
case,  act  as  a parachute,  and  as  such  might  be  purposely  de- 
tached from  the  cord,  which  then  being  sustained  from  the 
upper  kite,  could  be  easily  recovered.  The  direction  of  de- 
scent could  be  commanded  by  the  guy-ropes,  these  being  hauled 
taut  in  the  required  direction  for  landing. 

The  author  has  good  reasons  for  believing  that  there  would 
be  less  risk  associated  with  the  employment  of  this  apparatus, 
than  the  reconnoitring  balloons  that  have  now  frequently  been 
made  use  of  in  warfare.^ 

’ The  practical  application  of  these  suggestions  appears  to  have  been  anticipated  some 
years  previously.  In  a small  work,  styled  the  " History  of  the  Charvolant,  or  Kite  Car- 
riage," published  by  Longman  and  Co.,  appear  the  following  remarks  : — " These  buoyant 
sails,  possessing  immense  power,  will,  as  we  have  before  remarked,  serve  for  floating 
observatories.  . . . Elevated  in  the  air,  a single  sentinel,  with  a perspective,  could 
watch  and  report  the  advance  of  the  most  powerful  forces,  while  yet  at  a great  distance. 
He  could  mark  their  line  of  march,  the  composition  of  their  force,  and  their  general 
strength,  long  before  he  could  be  seen  by  the  enemy.”  Again,  at  page  53,  we  have  an 
account  of  ascents  actually  made,  as  follows : — “Nor  was  less  progress  made  in  the  experi- 
mental department,  when  large  weights  were  required  to  be  raised  or  transposed.  While 
on  this  subject,  we  must  not  omit  to  observe  that  the  first  person  who  soared  aloft  in  the 
air  by  this  invention  was  a lady,  whose  courage  would  not  be  denied  this  test  of  its  strength. 
An  arm-chair  was  brought  on  the  ground,  then  lowering  the  cordage  of  the  kite  by  slacken- 
ing the  lower  brace,  the  chair  was  firmly  lashed  to  the  mainline,  and  the  lady  took  her  seat. 
The  main-brace  being  hauled  taut,  the  huge  buoyant  sail  rose  aloft  with  its  fair  burden,  con- 
tinuing to  ascend  to  the  height  of  100  yards.  On  descending,  she  expressed  herself  much 
pleased  with  the  easy  motion  of  the  kite,  and  the  delightful  prospect  she  had  enjoyed. 
Soon  after  this,  another  experiment  of  a similar  nature  took  place,  when  the  inventor’s  son 
successfully  carried  out  a design  not  less  safe  than  bold ; that  of  scaling,  by  this  powerful 
aerial  machine,  the  brow  of  a cliff  200  feet  in  perpendicular  height.  Here,  after  safely  land- 
ing, he  again  took  his  seat  in  a chair  expressly  prepared  for  the  purpose,  and,  detaching  the 
swivel-line,  which  kept  it  at  its  elevation,  glided  gently  dotvn  the  cordage  to  the  hand  of  the 
director.  The  buoyant  sail  employed  on  this  occasion  was  thirty  feet  in  height,  with  a 
proportionate  spread  of  canvas.  The  rise  of  the  machine  was  most  majestic,  and  nothing 
could  surpass  the  steadiness  with  which  it  was  manoeuvred ; the  certainty  with  which  it 
answered  the  action  of  the  braces,  and  the  ease  with  which  its  power  was  lessened  or 
increased.  . . . Subsequently  to  this,  an  experiment  of  a very  bold  and  novel  character 


196 


THE  AERONAUTICAL  ANNUAL. 


The  wings  of  all  flying  creatures,  whether  of  birds,  bats, 
butterflies,  or  other  insects,  have  this  one  peculiarity  of  struct- 
ure in  common.  The  front,  or  leading  edge,  is  rendered  rigid 
by  bone,  cartilage,  or  a thickening  of  the  membrane ; and  in 
most  birds  of  perfect  flight,  even  the  individual  feathers  are 
formed  upon  the  same  condition.  In  consequence  of  this, 
when  the  wing  is  waved  in  air,  it  gives  a persistent  force  in  one 
direction,  caused  by  the  elastic  reaction  of  the  following  portion 
of  the  edge.  The  fins  and  tails  of  fishes  act  upon  the  same 
principle.  In  the  most  rapid  swimmers  these  organs  are  termed 
“ lobated  and  pointed.”  The  tail  extends  out  very  wide  trans- 
versely to  the  body,  so  that  a powerful  impulse  is  obtained 
against  a wide  stratum  of  water,  on  the  condition  before  ex- 
plained. This  action  is  imitated  in  Macintosh’s  screw-pro- 
peller, the  blade  of  which  is  made  of  thin  steel,  so  as  to  be 
elastic.  While  the  vessel  is  stationary,  the  blades  are  in  a line 
with  the  keel,  but  during  rotation  they  bend  on  one  side,  more 
or  less,  according  to  the  speed  and  degree  of  propulsion  re- 
quired, and  are  thus  self-compensating;  and  could  practical 
difficulties  be  overcome,  would  prove  to  be  a form  of  propeller 
perfect  in  theory. 

In  the  flying  mechanism  of  beetles  there  is  a difference  of 
arrangement.  When  the  elytra,  or  wing-cases,  are  opened, 
they  are  checked  by  a stop,  which  sets  them  at  a fixed  angle. 
It  is  probable  that  these  serve  as  “ aeroplanes,”  for  carrying  the 
weight  of  the  insect,  while  the  delicate  membrane  that  folds 
beneath  acts  more  as  a propelling  than  a supporting  organ.  A 
beetle  cannot  fly  with  the  elytra  removed. 

The  wing  of  a bird,  or  bat,  is  both  a supporting  and  propel- 

was  made  upon  an  extensive  down,  where  a wagon  with  a considerable  load  was  drawn 
along,  whilst  this  huge  machine,  at  the  same  time,  carried  an  obsen’er  aloft  in  the  air, 
realising  almost  the  romance  of  flying." 

It  may  be  remarked  that  the  brace-lines  here  referred  to  were  conveyed  down  the  main- 
hne  and  managed  below ; but  it  is  evident  that  the  same  hnes  could  be  managed  with  equal 
facility  by  the  person  seated  in  the  car  above ; and  if  the  main-line  were  attached  to  a 
water-drag  instead  of  a wheeled  car,  the  adventurer  could  cross  rivers,  lakes,  or  bays,  with 
considerable  latitude  for  steering  and  selecting  the  point  of  landing,  by  hauling  on  the  port  or 
starboard  brace-lines  as  required.  And  from  the  uniformity  of  the  resistance  offered  by 
the  water-drag,  this  experiment  could  not  be  attended  with  any  greater  amount  of  risk  than 
a land  flight  by  the  same  means. 


WENHAM  ON  AERIAL  LOCOMOTION. 


197 


ling  organ,  and  flight  is  performed  in  a rapid  course,  as 
follows: — During  the  down-stroke  it  can  be  easily  imagined 
how  the  bird  is  sustained ; but  in  the  up-stroke,  the  weight  is 
also  equally  well  supported,  for  in  raising  the  wing,  it  is  slightly 
inclined  upwards  against  the  rapidly  passing  air,  and  as  this 
angle  is  somewhat  in  excess  of  the  motion  due  to  the  raising 
of  the  wing,  the  bird  is  sustained  as  much  during  the  up  as  the 
down-stroke  — in  fact,  though  the  wing  may  be  rising,  the  bird 
is  still  pressing  against  the  air  with  a force  equal  to  the  weight 
of  its  body.  The  faculty  of  turning  up  the  wing  may  be  easily 
seen  when  a large  bird  alights ; for  after  gliding  down  its  aerial 
gradient,  on  its  approach  to  the  ground  it  turns  up  the  plane  of 
its  wing  against  the  air;  this  checks  its  descent,  and  it  lands 
gently. 

It  has  before  been  shown  how  utterly  inadequate  the  mere 
perpendicular  impulse  of  a plane  is  found  to  be  in  supporting 
a weight,  when  there  is  no  horizontal  motion  at  the  time. 
There  is  no  material  weight  of  air  to  be  acted  upon,  and  it 
yields  to  the  slightest  force,  however  great  the  velocity  of 
impulse  may  be.  On  the  other  hand,  suppose  that  a large 
bird,  in  full  flight,  can  make  forty  miles  per  hour,  or  3,520  feet 
per  minute,  and  performs  one  stroke  per  second.  Now,  during 
every  fractional  portion  of  that  stroke,  the  wing  is  acting  upon 
and  obtaining  an  impulse  from  a fresh  and  undisturbed  body 
of  air ; and  if  the  vibration  of  the  wing  is  limited  to  an  arc  of 
two  feet,  this  by  no  means  represents  the  small  force  of  action 
that  would  be  obtained  when  in  a stationary  position,  for  the 
impulse  is  secured  upon  a stratum  of  fifty-eight  feet  in  length 
of  air  at  each  stroke.  So  that  the  conditions  of  weight  of  air 
for  obtaining  support  equally  well  apply  to  weight  of  air,  and 
its  reaction  in  producing  forward  impulse. 

So  necessary  is  the  acquirement  of  this  horizontal  speed, 
even  in  commencing  flight,  that  most  heavy  birds,  when  pos- 
sible, rise  against  the  wind,  and  even  run  at  the  top  of  their 
speed  to  make  their  wings  available,  as  in  the  example  of  the 
eagle,  mentioned  at  the  commencement  of  this  paper.  It  is 
stated  that  the  Arabs,  on  horseback,  can  approach  near  enough 


198 


THE  AERONAUTICAL  ANNUAL. 


to  spear  these  birds,  when  on  the  plain,  before  they  are  able  to 
rise : their  habit  is  to  perch  on  an  eminence,  where  possible. 

The  tail  of  a bird  is  not  necessary  for  flight.  A pigeon  can 
fly  perfectly  with  this  appendage  cut  short  off:  it  probably  per- 
forms an  important  function  in  steering,  for  it  is  to  be  remarked, 
that  most  birds  that  have  either  to  pursue  or  evade  pursuit  are 
amply  provided  with  this  organ. 

The  foregoing  reasoning  is  based  upon  facts,  which  tend  to 
show  that  the  flight  of  the  largest  and  heaviest  of  all  birds  is 
really  performed  with  but  a small  amount  of  force,  and  that 
man  is  endowed  with  sufflcient  muscular  power  to  enable  him 
also  to  take  individual  and  extended  flights,  and  that  success 
is  probably  only  involved  in  a question  of  suitable  mechanical 
adaptations.  But  if  the  wings  are  to  be  modelled  in  imitation 
of  natural  examples,  but  very  little  consideration  will  serve 
to  demonstrate  its  utter  impracticability  when  applied  in  these 
forms.  The  annexed  diagram.  Fig.  i,  would  be  about  the  pro- 
portions needed  for  a man  of  medium  weight.  The  wings,  a a, 
must  extend  out  sixty  feet  from  end  to  end,  and  measure  four 
feet  across  the  broadest  part.  The  man,  b,  should  be  in  a hori- 
zontal position,  encased  in  a strong  framework,  to  which  the 
wings  are  hinged  at  c c.  The  wings  must  be  stiffened  by  elastic 
ribs,  extending  back  from  the  pinions.  These  must  be  trussed 
by  a thin  band  of  steel,  e e,  Fig.  2,  for  the  purpose  of  diminish- 
ing the  weight  and  thickness  of  the  spar.  At  the  front,  where 
the  pinions  are  hinged,  there  are  two  levers  attached,  and  drawn 
together  by  a spiral  spring,  d.  Fig.  2,  the  tension  of  which  is 
sufficient  to  balance  the  weight  of  the  body  and  machine,  and 
cause  the  wings  to  be  easily  vibrated  by  the  movement  of  the 
feet  acting  on  treadles.  This  spring  serves  the  purpose  of  the 
pectoral  muscles  in  birds.  But  with  all  such  arrangements 
the  apparatus  must  fail  — length  of  wing  is  indispensable ! and  a 
spar  thirty  feet  long  must  be  strong,  heavy,  and  cumbrous ; to 
propel  this  alone  through  the  air,  at  a high  speed,  would  require 
more  power  than  any  man  could  command. 

In  repudiating  all  imitations  of  natural  wings,  it  does  not 
follow  that  the  only  channel  is  closed  in  which  flying  mechanism 


WENHAM  ON  AERIAL  LOCOMOTION. 


199 


200 


THE  AERONAUTICAL  ANNUAL. 


may  prove  successful.  Though  birds  do  fly  upon  deflnite 
mechanical  principles,  and  with  a moderate  exertion  of  force, 
yet  the  wing  must  necessarily  be  a vital  organ  and  member  of 
the  living  body.  It  must  have  a marvellous  self-acting  principle 
of  repair,  in  case  the  feathers  are  broken  or  torn ; it  must  also 
fold  up  in  a small  compass,  and  form  a covering  for  the  body. 

These  considerations  bear  no  relation  to  artificial  wings ; so 
in  designing  a flying-machine,  any  deviations  are  admissible, 
provided  the  theoretical  conditions  involved  in  flight  are  borne 
in  mind. 

Having  remarked  how  thin  a stratum  of  air  is  displaced  be- 
neath the  wings  of  a bird  in  rapid  flight,  it  follows  that  in  order 
to  obtain  the  necessary  length  of  plane  of  supporting  heavy 
weights,  the  surfaces  may  be  superposed,  or  placed  in  parallel 
rows,  with  an  interval  between  them.  A dozen  pelicans  may 
fly  one  above  the  other  without  mutual  impediment,  as  if  framed 
together;  and  it  is  thus  shown  how  two  hundred  weight  may 
be  supported  in  a transverse  distance  of  only  ten  feet. 

In  order  to  test  this  idea,  six  bands  of  stiff  paper,  three  feet 
long  and  three  inches  wide,  were  stretched  at  a slight  upward 
angle,  in  a light  rectangular  frame,  with  an  interval  of  three 
inches  between  them,  the  arrangement  resembling  an  open 
Venetian  blind.  When  this  was  held  against  a breeze,  the  lift- 
ing power  was  very  great,  and  even  by  running  with  it  in  a calm 
it  required  much  force  to  keep  it  down.  The  success  of  this 
model  led  to  the  construction  of  one  of  a sufficient  size  to  carry 
the  weight  of  a man.  Fig.  3 represents  the  arrangement,  a a is 
a thin  plank,  tapered  at  the  outer  ends,  and  attached  at  the  base 
to  a triangle,  b,  made  of  similar  plank,  for  the  insertion  of  the 
body.  The  boards,  a a,  were  trussed  with  thin  bands  of  iron,  c c, 
and  at  the  ends  were  vertical  rods,  d d.  Between  these  were 
stretched  five  bands  of  holland,  fifteen  inches  broad  and  sixteen 
feet  long,  the  total  length  of  the  web  being  eighty  feet.  This 
was  taken  out  after  dark  into  a wet  piece  of  meadow  land,  one 
November  evening,  during  a strong  breeze,  wherein  it  became 
quite  unmanageable.  The  wind  acting  upon  the  already  tightly- 
stretched  webs,  their  united  pull  caused  the  central  boards  to 


WENHAM  ON  AERIAL  LOCOMOTION. 


201 


bend  considerably,  with  a twisting,  vibratory  motion.  During  a 
lull,  the  head  and  shoulders  were  inserted  in  the  triangle,  with 
the  chest  resting  on  the  base  board.  A sudden  gust  caught  up 
the  experimenter,  who  was  carried  some  distance  from  the 
ground,  and  the  affair  falling  over  sideways,  broke  up  the  right- 
hand  set  of  webs. 

In  all  new  machines  we  gain  experience  by  repeated  failures, 
which  frequently  form  the  stepping-stones  to  ultimate  success. 
The  rude  contrivance  just  described  (which  was  but  the  work 
of  a few  hours)  had  taught,  first,  that  the  webs,  or  aeroplanes, 
must  not  be  distended  in  a frame,  as  this  must  of  necessity  be 
strong  and  heavy,  to  withstand  their  combined  tension  ; second, 
that  the  planes  must  be  made  so  as  either  to  furl  or  fold  up,  for 
the  sake  of  portability. 

In  order  to  meet  these  conditions,  the  following  arrangement 
was  afterwards  tried : — a a.  Figs.  4 and  5,  is  the  main  spar,  six- 
teen feet  long,  half  an  inch  thick  at  the  base,  and  tapered,  both 
in  breadth  and  thickness,  to  the  end ; to  this  spar  was  fastened 
the  panels  b b,  having  a base-board  for  the  support  of  the  body. 
Under  this,  and  fastened  to  the  end  of  the  main  spar,  is  a thin 
steel  tie-band,  e e,  with  struts  starting  from  the  spar.  This 
served  as  the  foundation  of  the  superposed  aeroplanes,  and, 
though  very  light,  was  found  to  be  exceedingly  strong;  for 
when  the  ends  of  the  spar  were  placed  upon  supports,  the 
middle  bore  the  weight  of  the  body  without  any  strain  or  de- 
flection ; and  further,  by  a separation  at  the  base-board,  the 
spars  could  be  folded  back,  with  a hinge,  to  half  their  length. 
Above  this  were  arranged  the  aeroplanes,  consisting  of  six  webs 
of  thin  holland,  fifteen  inches  broad ; these  were  kept  in  parallel 
planes,  by  vertical  divisions,  two  feet  wide,  of  the  same  fabric, 
so  that  when  distended  by  a current  of  air,  each  two  feet  of  web 
pulled  in  opposition  to  its  neighbour;  and  finally,  at  the  ends 
(which  were  each  sewn  over  laths) , a pull  due  to  only  two  feet  had 
to  be  counteracted,  instead  of  the  strain  arising  from  the  entire 
length,  as  in  the  former  experiment.  The  end-pull  was  sustained 
by  vertical  rods,  sliding  through  loops  on  the  transverse  ones  at 
the  ends  of  the  webs,  the  whole  of  which  could  fall  flat  on  the 


202 


THE  AERONAUTICAL  ANNUAL. 


spar,  till  raised  and  distended  by  a breeze.  The  top  was 
stretched  by  a lath,  y,  and  the  system  kept  vertical  bystaycords, 
taken  from  a bowsprit  carried  out  in  front,  shown  in  Fig.  6.  All 
the  front  edges  of  the  aeroplanes  were  stiffened  by  bands  of 
crinoline  steel.  This  series  was  for  the  supporting  arrangement, 
being  equivalent  to  a length  of  wing  of  ninety-six  feet.  Exterior 
to  this,  two  propellers  were  to  be  attached,  turning  on  spindles 
just  above  the  back.  They  are  kept  drawn  up  by  a light  spring, 
and  pulled  down  by  cords  or  chains,  running  over  pulleys  in  the 
panels  b b,  and  fastened  to  the  end  of  a swivelling  cross-yoke, 
sliding  on  the  base-board.  By  working  this  cross-piece  with  the 
feet,  motion  will  be  communicated  to  the  propellers,  and  by 
giving  a longer  stroke  with  one  foot  than  the  other,  a greater 
extent  of  motion  will  be  given  to  the  corresponding  propeller, 
thus  enabling  the  machine  to  turn,  just  as  oars  are  worked  in  a 
rowing  boat.  The  propellers  act  on  the  same  principle  as  the 
wing  of  a bird  or  bat : their  ends  being  made  of  fabric,  stretched 
by  elastic  ribs,  a simple  waving  motion  up  and  down  will  give  a 
strong  forward  impulse.  In  order  to  start,  the  legs  are  lowered 
beneath  the  base-board,  and  the  experimenter  must  run  against 
the  wind. 

An  experiment  recently  made  with  this  apparatus  developed 
a cause  of  failure.  The  angle  required  for  producing  the 
requisite  supporting  power  was  found  to  be  so  small,  that  the 
crinoline  steel  would  not  keep  the  front  edges  in  tension.  Some 
of  them  were  borne  downwards  and  more  on  one  side  than  the 
other,  by  the  operation  of  the  wind,  and  this  also  produced  a 
strong  fluttering  motion  in  the  webs,  destroying  the  integrity  of 
their  plane  surfaces,  and  fatal  to  their  proper  action. 

Another  arrangement  has  since  been  constructed,  having  laths 
sewn  in  both  edges  of  the  webs,  which  are  kept  permanently 
distended  by  cross-stretchers.  All  these  planes  are  hinged  to 
a vertical  central  board,  so  as  to  fold  back  when  the  bottom  ties 
are  released,  but  the  system  is  much  heavier  than  the  former 
one,  and  no  experiments  of  any  consequence  have  as  yet  been 
tried  with  it. 

It  may  be  remarked  that  although  a principle  is  here  defined. 


WENHAM  ON  AERIAL  LOCOMOTION. 


203 


yet  considerable  difficulty  is  experienced  in  carrying  the  theory 
into  practice.  When  the  wind  approaches  to  fifteen  or  twenty 
miles  per  hour,  the  lifting  power  of  these  arrangements  is  all 
that  is  requisite,  and,  by  additional  planes,  can  be  increased  to 
any  extent ; but  the  capricious  nature  of  the  ground-currents  is 
a perpetual  source  of  trouble. 

Great  weight  does  not  appear  to  be  of  much  consequence,  if 
carried  in  the  body ; but  the  aeroplanes  and  their  attachments 
seem  as  if  they  were  required  to  be  very  light,  otherwise,  they 
are  awkward  to  carry,  and  impede  the  movements  in  running 
and  making  a start.  In  a dead  calm,  it  is  almost  impracticable 
to  get  sufficient  horizontal  speed,  by  mere  running  alone,  to 
raise  the  weight  of  the  body.  Once  off  the  ground,  the  speed 
must  be  an  increasing  one,  if  continued  by  suitable  propellers. 
The  small  amount  of  experience  as  yet  gained,  appears  to  in- 
dicate that  if  the  aeroplanes  could  be  raised  in  detail,  like  a 
superposed  series  of  kites,  they  would  first  carry  the  weight  of 
the  machine  itself,  and  next  relieve  that  of  the  body. 

Until  the  last  few  months  no  substantial  attempt  has  been 
made  to  construct  a flying-machine,  in  accordance  with  the 
principle  involved  in  this  paper,  which  was  written  seven  years 
ago.  The  author  trusts  that  he  has  contributed  something 
towards  the  elucidation  of  a new  theory,  and  shown  that  the 
flight  of  a bird  in  its  performance  does  not  require  that  enor- 
mous amount  of  force  usually  supposed,  and  that  in  fact  birds 
do  not  exert  more  power  in  flying  than  quadrupeds  in  running, 
but  considerably  less  ; for  the  wing  movements  of  a large  bird, 
travelling  at  a far  higher  speed  in  air,  are  very  much  slower ; 
and,  where  weight  is  concerned,  great  velocity  of  action  in  the 
locomotive  organs  is  associated  with  great  force. 

It  is  to  be  hoped  that  further  experiments  will  confirm  the 
correctness  of  these  observations,  and  with  a sound  working 
theory  upon  which  to  base  his  operations,  man  may  yet  com- 
mand the  air  with  the  same  facility  that  birds  now  do. 

The  Chairman:  “ I think  the  paper  just  read  is  one  of  great 
interest  and  importance,  especially  as  it  points  out  the  true 
mechanical  explanation  of  the  curious  problem,  as  to  how  and 


204 


THE  AERONAUTICAL  ANNUAL. 


why  it  is  that  birds  of  the  most  powerful  flight  always  have  the 
longest  and  narrowest  wings.  I think  it  quite  certain,  that  if 
the  air  is  ever  to  be  navigated,  it  will  not  be  by  individual  men 
flying  by  means  of  machinery;  but  that  it  is  quite  possible  ves- 
sels may  be  invented,  which  will  carry  a number  of  men,  and 
the  motive  force  of  which  will  not  be  muscular  action.  VVe 
must  first  ascertain  clearly  the  mechanical  principles  upon 
which  flight  is  achieved ; and  this  is  a subject  which  has 
scarcely  ever  been  investigated  in  a scientific  spirit.  In  fact, 
you  will  see  in  our  best  works  of  science,  by  the  most  distin- 
guished men,  the  account  given  of  the  anatomy  of  birds  is,  that 
a bird  flies  by  inflating  itself  with  warm  air,  by  which  it  becomes 
buoyant,  like  a balloon.  The  fact  is,  however,  that  a bird  is 
never  buoyant.  A bird  is  immensely  heavier  than  the  air. 
We  all  know  that  the  moment  a bird  is  shot  it  falls  to  the  earth ; 
and  it  must  necessarily  do  so,  because  one  of  the  essential 
mechanical  principles  of  flight  is  weight,  without  it  there  can 
be  no  momentum,  and  no  motive  force  capable  of  moving 
through  atmospheric  currents. 

“ Until  I read  Mr.  Wenham’s  paper,  a few  weeks  since,  I was 
puzzled  by  the  fact,  that  birds  with  long  and  very  narrow  wings 
seem  to  be  not  only  as  efficient  fliers,  but  much  more  efficient 
fliers  than  birds  with  very  large,  broad  wings.  If  you  observe 
the  flight  of  the  common  heron  — which  is  a bird  with  a very 
large  wing,  disposed  rather  in  breadth  than  in  length  — you 
will  notice  that  it  is  exceedingly  slow,  and  that  it  has  a very 
heavy,  flapping  motion.  The  common  swallow,  on  the  other 
hand,  is  provided  with  a long  and  narrow  wing,  and  I never 
understood  how  it  was  that  long-winged  birds,  such  as  these, 
achieved  so  rapid  a flight,  until  I read  Mr.  Wenham’s  paper. 
Although  I do  not  profess  to  be  able  to  follow  the  elaborate 
calculations  which  he  has  laid  before  us,  I think  I now  under- 
stand the  explanation  he  has  given.  His  explanation  of  the 
action  of  narrow  wings  upon  the  air  is,  that  it  is  precisely  like  the 
action  of  the  narrow  vanes  of  the  ship’s  screw  in  water,  and  that 
the  resisting  power  of  the  screw  is  the  same,  or  nearly  the  same. 


WENHAM  ON  AERIAL  LOCOMOTION. 


205 


whether  you  have  the  total  area  of  revolution  covered  by  solid 
surface,  or  traversed  by  long  and  narrow  vanes  in  rotation. 

“ If  Mr.  Wenham’s  explanation  be  nearly  correct,  that  sup 
posing  this  implement  (referring  to  a model)  to  be  carried  for- 
ward by  some  propelling  power,  the  sustaining  force  of  the 
whole  area  is  simply  the  sustaining  force  of  the  narrow  band  in 
front.  This,  however,  is  a matter  which  will  have  to  be  decided 
by  experiment.  It  certainly  appears  to  explain  the  phenomena 
of  the  flight  of  birds.  There  are  one  or  two  observations  in  the 
paper  I do  not  quite  agree  with.  Although  I have  studied  the 
subject  for  many  years,  I have  not  arrived  at  Mr.  Wenham’s 
conclusion  that  the  upward  stroke  of  a bird’s  wing  has  precisely 
the  same  effect  as  a downward  stroke  in  sustaining.  An  upward 
stroke  has  a contrary  effect  to  the  downward  stroke ; it  has  a 
propelling  power  certainly,  but  I believe  that  the  sustaining 
power  of  a bird’s  flight  is  due  entirely  to  the  downward  stroke. 
I should  be  glad  to  hear  what  Mr.  Wenham  may  have  to  say 
upon  this.  My  belief  is,  that  an  upward  stroke  must  have,  so 
far  as  sustaining  is  concerned,  a reverse  action  to  the  downward 
stroke. 

“ Then  with  regard  to  another  observation  of  Mr.  Wenham’s, 
that  the  tails  of  birds  are  used  as  rudders.  I believe  this  to 
be  an  entire  mistake ; for  if  the  tail  of  a bird  could  have  the 
slightest  effect  in  guiding,  the  vane  of  it  must  be  disposed  per- 
pendicularly, and  not  horizontally,  or  nearly  so,  as  at  present. 

“ If  you  cut  off  the  tail  of  a pigeon,  you  will  find  that  he  can 
fly  and  turn  perfectly  well  without  it.  He  may  be  a little  awk- 
ward about  it  at  first,  but  that  is  because  he  has  lost  his  balanc- 
ing power.  We  all  know  that  it  is  a common  thing  to  see  a 
sparrow  without  his  tail,  therefore,  I do  not  in  the  least  believe 
that  tails  have  any  effect  in  guiding.  They  have  an  important 
effect  in  stopping  progress,  and,  undoubtedly,  that  is  one  of  the 
necessary  elements  of  turning.  If  a bird  comes  close  over  your 
head,  and  is  frightened,  you  will  find  his  claws  distended  and 
his  tail  spread  out  as  a fan,  to  stop  the  momentum  of  his  flight. 
These  are  the  two  only  observations  with  which  I cannot  agree ; 
but  as  regards  the  explanation  he  has  given  as  to  the  resistance 


2o6 


THE  AERONAUTICAL  ANNUAL. 


offered  by  long  and  narrow  wings,  he  has  made  an  important 
discovery.” 

Mr.  Wenham;  “With  regard  to  the  wing  not  affording  sup- 
port to  the  bird  during  the  upward  stroke,  some  of  the  largest 
birds  move  their  wings  slowly,  that  is,  with  a less  number  than 
sixty  strokes  per  minute.  Now,  as  a body  free  to  fall  must 
descend  fifteen  feet  in  one  second,  whether  in  horizontal  motion 
or  not,  it  appears  clear  to  me  that  there  must  be  some  counter- 
acting effect  to  prevent  this  fall.  When  the  wing  has  reached 
the  limit  of  the  down-stroke,  it  is  inclined  upwards  in  the  direc- 
tion of  motion,  consequently  the  rush  of  air  caused  by  the  for- 
ward speed,  weight,  and  momentum  of  the  bird  against  the 
under  surface  of  the  wing,  supports  the  weight,  even  though  the 
wing  is  rising  in  the  up-stroke  at  the  time.  In  corroboration  of 
my  theory,  I will  read  an  extract  from  Sir  George  Cayley,  who 
made  a large  number  of  experiments.  He  says,  in  page  83,  of 
Vol.  XXV.,  ‘Nicholson’s  Journal’ : — ‘The  stability  in  this  posi- 
tion, arising  from  the  centre  of  gravity,  being  below  the  point 
of  suspension,  is  aided  by  a remarkable  circumstance  that 
experiment  alone  could  point  out.  In  very  acute  angles  with 
the  current,  it  appears  that  the  centre  of  resistance  in  the  sail 
does  not  coincide  with  the  centre  of  its  surface,  but  is  consider- 
ably in  front  of  it.  As  the  obliquity  of  the  current  decreases, 
these  centres  approach  and  coincide  when  the  current  becomes 
perpendicular  to  the  plane,  hence  any  heel  of  the  machine 
backwards  or  forwards  removes  the  centre  of  support  behind 
or  before  the  point  of  suspension.’ 

“ From  this  discovery,  it  seems  remarkable  that  Sir  George 
Cayley,  finding  that  at  high  speeds  with  very  oblique  incidences 
the  supporting  effect  became  transferred  to  the  front  edge,  the 
idea  should  not  have  occurred  to  him  that  a narrow  plane,  with 
its  long  edge  in  the  direction  of  motion,  would  have  been 
equally  effective.  I may  give  another  illustration.  We  all  know, 
from  our  schoolboy  experience,  that  ice  which  would  not  be 
safe  to  stand  upon,  is  found  to  be  quite  strong  enough  to  bear 
heavy  bodies  passing  over  it,  so  long  as  rapid  motion  is  kept  up, 
and  then  it  will  not  even  crack.  We  know,  also,  that  in  driving 


WENHAM  ON  AERIAL  LOCOMOTION. 


207 


through  a marshy  part  of  road,  in  which  you  expect  the  wheels 
to  sink  in  up  to  the  axles,  you  may  pass  over  much  more  easily 
by  increasing  the  speed.  In  both  these  examples  there  is  a 
greater  weight  passed  over  in  a given  time,  and  consequently  a 
better  support  obtained.  The  ice  will  not  become  deflected ; 
neither  has  the  mud  time  to  give  way.  At  a slow  speed  the 
same  effect  may  be  obtained  by  extending  the  breadth  of  the 
wheel.  Thus,  suppose  an  ordinary  wheel  to  sink  ten  inches,  if 
you  double  this  width  it  will  sink  only  five  inches ; and  so  on, 
until  by  extending  the  wheel  into  a long  roller  you  may  pass 
over  a quicksand  with  perfect  safety.  Now,  Nature  has  carried 
out  this  principle  in  the  long  wings  of  birds,  and  in  the  albatross 
it  is  seen  in  perfection.” 


(^Extracts  from  the  “ Technology  Review,”  Afril,  igio.') 

THE  BLUE  HILL  METEOROLOGICAL  OBSERVATORY. 

1885-1910. 


When  a private  scientific  establishment  has  completed  an 
existence  of  a quarter  of  a century,  it  may  be  considered  as  a 
permanent  institution  and  as  such  worthy  of  public  notice. 

The  Blue  Hill  Meteorological  Observatory  was  founded  in 
1885  by  A.  Lawrence  Rotch.^ 

The  earliest  measurements  in  America  of  the  height  and  ve- 
locity of  clouds,  by  trigonometrical  and  other  methods,  were 
made  at  Blue  Hill  in  1890-91,  and  were  repeated  in  1896-97 
as  part  of  an  international  system.  These  researches  and  the 
first  applications  of  kites  in  1894,  at  the  suggestion  of  Mr.  W. 
A.  Eddy,  to  obtain  meteorological  observations  in  the  upper  air 
by  means  of  instruments,  recording  graphically  and  continuously, 
made  the  Observatory  widely  known.  The  use  of  cellular  kites 
flown  with  steel  wire  and  controlled  by  a power  windlass  orig- 
inated at  Blue  Hill,  and  was  subsequently  adopted  by  the  United 
States  Weather  Bureau  and  many  stations  abroad. 

In  1899  kites  were  used  to  elevate  the  terminal  wires  in 
experiments  in  wireless  telegraphy  between  Blue  Hill  and 
Cambridge.  In  1901  Professor  Rotch  and  Mr.  Sweetland  made 
a transatlantic  voyage  to  demonstrate  that  kites  might  be  flown 
at  sea  in  calm  weather  by  utilizing  the  motion  of  the  vessel  to 
create  an  artificial  wind.  A more  complete  exploration  of  the 
air  over  the  ocean  by  this  method  was  made  by  Mr.  Clayton  in 
a voyage  to  Gibraltar  in  1905,  after  which,  on  a steam  yacht 
sent  to  the  equatorial  Atlantic  through  the  cooperation  with 
Mr.  Rotch  of  a French  colleague,  M.  Teisserenc  de  Bort,  both 
kites  and  pilot-balloons  were  used  to  investigate  the  trade- 
winds.  The  unprecedented  height  of  three  miles  was  reached 
by  kites  at  Blue  Hill  in  1900,  and  kite  flights  are  still  made 
there  once  a month. 


^ See  page  149. 
(208) 


THE  BLUE  HILL  METEOROLOGICAL  OBSERVATORY.  20g 


To  obtain  temperatures  at  much  greater  heights,  free  balloons 
carrying  self-recording  instruments  were  employed  for  the  first 
time  in  this  country  by  Professor  Rotch  during  the  St.  Louis 
Exposition.  In  this  and  the  following  four  years,  of  the  seventy- 
six  balloons  sent  up  from  St.  Louis,  seventy-two  were  recov- 
ered. The  heights  occasionally  exceeded  ten  miles,  and  a 
temperature  of  lll°  F.  below  zero  was  registered,  which  is  one 
of  the  lowest  natural  temperatures  ever  observed.  Such  sound- 
ing balloons  sent  up  by  Professor  Rotch  from  Pittsfield,  Mass., 
are  not  so  often  recovered,  but  pilot-balloons,  followed  by 
theodolites  from  Blue  Hill,  permit  the  direction  and  speed  of 
the  upper  currents  to  be  determined  up  to  great  heights  in 
this  region. 

Aerological  observations,  as  those  in  the  free  air  are  called, 
are  now  conducted  at  many  stations  throughout  the  world, 
and  it  is  obvious  that  such  observations,  while  undertaken  in 
the  interest  of  pure  science,  have  a prospective  value  for  aerial 
navigation,  and  it  is  probable  that  a station  like  Blue  Hill, 
which  already  has  counterparts,  both  government  and  private, 
will  be  necessary  in  each  region  to  ascertain  the  conditions 
which  may  be  expected  to  be  encountered  at  different  heights 
in  the  atmosphere  by  aerial  craft. 

Professor  Rotch  has  been  ably  assisted  in  his  work.  Mr. 
S.  P.  Fergusson  joined  the  Observatory  staff  in  1887  and  is  still 
a member.  Mr.  H.  Helm  Clayton  was  a member  for  a period 
of  twenty-three  years,  with  some  interruptions.  His  investiga- 
tions have  brought  distinction  to  himself  and  the  Observatory. 
Mr.  A.  E.  Sweetland,  who  died  after  eight  years’  service,  was 
succeeded  in  1903  by  Mr.  L.  A.  Wells,  and  he,  together  with 
Mr.  Fergusson  and  Mr.  L.  H.  Palmer,  are  at  present  the  assist- 
ants of  Professor  Rotch,  who  assumes  the  direction  of  the  work 
and  the  burden  of  the  expense. 

The  purpose  of  the  Observatory  continues  to  be  mainly 
research,  free  from  prescribed  duties  and  independent  of  out- 
side control.  It  is,  however,  attached  to  Harvard  University, 
and  publication  is  made  in  the  Annals  of  the  Astronomical 
Observatory  of  Harvard  College.  The  building,  on  the  summit 


210 


THE  AERONAUTICAL  ANNUAL. 


of  Great  Blue  in  the  Metropolitan  Park  Reservation,  has 

been  three  times  enlarged,  and  the  annual  expense  has  been 
increased  to  $5,000  a year.  Perhaps  the  most  valuable  part  of 
the  equipment  is  a library  of  about  ten  thousand  books  and 
pamphlets.  To  avoid  interference  with  the  work,  the  Obser- 
vatory is  closed  to  the  public. 

The  value  of  a meteorological  record  increases  with  each 
year  of  observation,  and,  while  twenty-five  years  homogeneous 
observations  of  all  the  meteorological  elements  constitute  a 
unique  series  in  America,  it  is  still  too  short  a period  to  deter- 
mine secular  changes  of  climate.  Therefore  it  is  to  be  hoped 
that  the  Observatory  may  have  its  existence  prolonged,  with 
unchanged  environment  and  methods  of  observation,  to  the 
close  of  the  century;  but,  since  this  transcends  the  life  of  an 
individual,  the  duty  must  devolve  on  the  University  to  which  it 
is  allied. 


[From  Aero.  Ann.,  1897.] 


MISCELLANY. 


THE  ALBATROSS. 

The  contour  of  the  albatross,  shown  in  Plate  XVII.,  is  taken  from  Alfred 
Newton’s  “ Dictionary  of  Birds,”  and  the  following  quotation  comes  from  the 
same  source:  “In  process  of  time  the  name  has  become  definitely  limited 
to  the  larger  species  of  Diomedeidce,  a family  of  the  group  Tubinares,  and 
especially  to  the  largest  species  of  the  genus  Diomedea  exulans,  the  ‘Man-of- 
war  bird  ’ or  wandering  albatross  of  many  authors.  Of  this,  though  it  has 
been  so  long  the  observed  of  all  observers  among  voyagers  to  the  Southern 
Ocean,  no  one  seems  to  have  given,  from  the  life,  its  finished  portrait  on  the 
wing,  and  hardly  such  a description  as  would  enable  those  who  have  not  seen 
it  to  form  an  idea  of  its  look. 

“The  diagrammatic  sketch  by  Captain  (now  Professor)  Hutton,  here  in- 
troduced, is  probably  a more  correct  representation  of  it  than  can  be  found  in 
the  conventional  figures  which  abound  in  books.  The  ease  with  which  this 
bird  maintains  itself  in  the  air,  ‘sailing’  for  a long  while  without  any  per- 
ceptible motion  of  its  wings,  whether  gliding  over  the  billows,  or  boldly 
shooting  aloft,  again  to  descend  and  possibly  alight  on  the  surface,  has  been 


*The  summit  is  10.4  miles  S.S.W.  from  the  Massachusetts  State  House  in  Boston. 
Travellers  from  New  York  to  Boston,  via  Providence,  may  see  the  Observatory  on  the 
right,  about  fifteen  minutes  before  reaching  Boston.  See  Illustration,  Plate  XIV. 


MISCELLANY. 


2II 


dwelt  upon  often  enough,  as  has  its  capacity  to  perform  these  feats  equally  in  a 
seeming  calm  or  in  the  face  of  a gale  ; but  more  than  this  is  wanted,  and  one 
must  hope  that  a series  of  instantaneous  photographs  may  soon  be  obtained 
which  will  show  the  feathered  aeronaut  with  becoming  dignity. 

“The  most  vivid  description  is  perhaps  that  given  by  Mr.  Froude  in  his 
‘ Oceana,’  of  which  a part  may  here  be  quoted.  ‘ The  albatross  wheels  in 
circles  round  and  round,  and  forever  round  the  ship,  now  far  behind,  now 
sweeping  past  in  a long  rapid  curve,  like  a perfect  skater  on  an  untouched 
field  of  ice.  There  is  no  effort;  watch  as  closely  as  you  will,  you  rarely  or 
never  see  a stroke  of  the  mighty  pinion.  The  flight  is  generally  near  the 
water,  often  close  to  it.  You  lose  sight  of  the  bird  as  he  disappears  in  the 
hollow  between  the  waves,  and  catch  him  again  as  he  rises  over  the  crest; 
but  how  he  rises  and  whence  comes  the  propelling  force  is  to  the  eye  inex- 
plicable ; he  alters  merely  the  angle  at  which  the  wings  are  inclined ; usually 
they  are  parallel  to  the  water  and  horizontal,  but  when  he  turns  to  ascend,  or 
makes  a change  in  his  direction,  the  wings  then  point  at  an  angle,  one  to  the 
sky,  the  other  to  the  water.’ 

“The  mode  in  which  the  ‘ sailing  ’ of  the  albatross  is  effected  has  been  much 
discussed,  but  there  can  be  little  doubt  that  Professor  Hutton  is  right  in  de- 
claring (“Ibis,”  1865,  p.  296)  that  it  is  only  ‘by  combining,  according  to  the 
laws  of  mechanics,  this  pressure  of  the  air  against  his  wings  with  the  force 
of  gravity,  and  by  using  his  head  and  tail  as  bow  and  stern  rudders,  that  the 
albatross  is  enabled  to  sail  in  any  direction  be  pleases,  so  long  as  his  momen- 
tum lasts.’ 

“ Much  discrepancy,  at  present  inexplicable,  exists  in  the  accounts  given  by 
various  writers  of  the  expanse  of  wing  in  this  species.  We  may  set  aside  as 
a gross  exaggeration  the  assertion  that  examples  have  been  obtained  measur- 
ing 20  feet,  but  Dr.  George  Bennett,  of  Sydney,  states  that  he  has  ‘ never  seen 
the  spread  of  the  wings  greater  than  14  feet.’  Recently  Mr.  J.  F.  Green  says 
that,  out  of  more  than  one  hundred  which  he  had  caught  and  measured,  the 
largest  was  ii  feet  4 inches  from  tip  to  tip,  a statement  exactly  confirmed,  he 
adds,  by  the  forty  years’  experience  of  a ship-captain  who  had  always  made  a 
point  of  measuring  these  birds,  and  had  never  found  one  over  that  length. 

“ In  the  adult  bird  the  plumage  of  the  body  is  white,  more  or  less  mottled 
above  by  fine  wavy  bars,  and  the  quill  feathers  of  the  wings  are  brownish- 
black.  The  young  are  suffused  with  slaty  brown,  the  tint  becoming 
lighter  as  the  bird  grows  older.  It  is  found  throughout  the  Southern  Ocean, 
seldom  occurring  northward  of  latitude  30°  S.,  and  is  invariably  met  with  by 
ships  that  round  the  Cape  of  Good  Hope  or  pass  the  Strait  of  Magellan.” 

From  “ L’Empire  de  I’Air,”  by  Mouillard,  1881  (see  Smithsonian  Report, 
1892)  : 

“ The  most  stirring,  exciting  sight  (the  word  is  not  too  strong)  is  to  stand 
in  the  vulture  roost  on  the  Mokatan  ridge,  near  Cairo,  and  to  look  upon  the 
Gyps  fulvus  (tawny  vulture)  passing  within  five  yards  in  full  flight. 
. . . All  my  life  I shall  remember  the  first  flight  of  these  birds  which  I 

saw,  the  great  tawny  vultures  of  Africa.  I was  so  impressed  that  all  day  long 
I could  think  of  nothing  else;  and  indeed  there  was  good  cause,  for  it  was  a 
practical  perfect  demonstration  of  all  my  preconceived  theories  concerning 
the  possibilities  of  artificial  flight  in  a wind.  Since  then  I have  observed 
thousands  of  vultures.  I have  disturbed  many  of  the  vast  flocks  of  these 
birds,  and  yet,  even  now,  I cannot  see  one  individual  passing  through  the  air 
without  following  him  with  my  eyes  until  he  disappears  in  the  distant 
horizon.  . . . 

“The  vulture’s  needs  are  few,  and  his  strength  is  moderate.  To  earn  his 
living  he  but  needs  to  sight  the  dead  animal  from  afar.  And  so,  what  does 
he  know  1 He  knows  how  to  rise,  how  to  float  aloft,  to  sweep  the  field  with 
keen  vision,  to  sail  upon  the  wind  without  effort,  till  the  carcass  is  seen,  and 
then  to  descend  slowly  after  careful  reconnaissance  and  assurance  that  he  may 


212 


THE  AERONAUTICAL  ANNUAL. 


alight  without  danger,  that  he  will  not  be  surprised  and  compelled  to  pre- 
cipitous and  painful  departure.  And  so  he  has  evolved  a peculiar  mode  of 
flight ; he  sails  and  spends  no  force,  he  never  hurries,  he  uses  the  wind  instead 
of  his  muscles,  and  the  wing-flap  occasionally  seen  is  meant  to  limber  up 
rather  than  to  hasten  through  the  air.  And  so  the  true  model  to  study  is  the 
vulture — the  great  vulture.  Beside  him  the  stork  is  as  a wren,  the  kite  a 
mere  butterfly,  the  falcon  a pin-feather.  Whoso  has  for  five  minutes  had  the 
fortune  to  see  the  Nubian  vulture  in  full  sail  through  the  air,  and  has  not 
perceived  the  possibility  of  his  imitation  by  man,  is  — I will  not  say  of  dull 
understanding,  but  certainly  inapt  to  analyze  and  to  appreciate.”  ‘ 


As  to  sailing  flight,  none  of  the  old-time  falconers  doubted  in  the  least  its 
existence.  They  observed  it  every  day,  and  they  knew  that  the  wind  was  a 
necessary  condition.  Nobody  troubled  himself  about  an  explanation  in  those 
days;  but  later  on,  when  physicists  attempted  to  explain  the  mechanics  of 
flight  and  succeeded  in  conceiving  the  action  of  the  wing  stroke  and  the 
effects  of  air  resistances,  sailing  flight  appeared  to  them  as  a physical  impos- 
sibility. They  said  that  it  was  impossible  to  admit  that  a bird,  suspended  at 
a fixed  point  in  the  sky,  should  find  in  the  action  of  the  wind  sufficient  power 
to  advance  against  that  wind.  As  well,  said  they,  might  we  throw  an 
inert  mass  into  a flowing  river,  and  expect  the  current  to  cause  the  body  to 
advance  up-stream.  And  yet,  modern  observers  have  contested  this  verdict. 
M.  d’Esterno  and  M.  Mouillard  demonstrated  that,  unless  we  absolutely  dis- 
believe ocular  evidence,  we  must  accept  the  actual  fact  that  sailing  flight  is 
possible,  even  if  we  have  to  admit  that  our  present  mechanical  knowledge  is 
insufficient  to  explain  it.  — Marey.  hist,  of  France. 


Lilienthal  wrote  as  follows  under  date  of  April  17,  1896:  “I  am  now 

engaged  in  constructing  an  apparatus  in  which  the  position  of  the  wings 
can  be  changed  during  flight  in  such  a way  that  the  balancing  is  not  effected 
by  changing  the  position  of  the  centre  of  gravity  of  the  body.  In  my  opin- 
ion this  means  considerable  progress,  as  it  will  increase  the  safety.  This  will 
probably  cause  me  to  give  up  again  the  double  sailing  surfaces  as  it  will  do 
away  with  the  necessity  which  led  me  to  adopt  them.” 


Flapping  wings  may  be  imitated,  but  only  with  small  models  ; the  increased 
strength  and  weight  of  material  necessary  for  larger  apparatus,  and  the  great 
motive  power  required  for  alternative  action,  have  proved  to  be  obstacles  not 
yet  overcome.  — Mouillard,  18^4. 


We  must  not  allow  ourselves  to  be  deceived  as  to  the  form  of  the  bird’s 
wing.  It  is  always  more  curved  when  not  spread  than  when  the  bird 
is  resting  its  weight  upon  it  in  the  air.  Besides  which,  the  curve,  which  in 
the  beginning  appears  to  be  considerably  stronger  towards  the  front  edge, 
becomes  somewhat  more  uniform  as  soon  as  the  quills  are  bent  straighter  at 
their  roots  by  the  pressure  of  the  air  from  beneath. — Lilienthal,  March,  iSgy. 


My  investigations  concerning  the  effects  of  curved  wings  had  one  result 
which  was  quite  unexpected,  namely,  that  the  air  resistance  is  not  perpendic- 


r Mouillard  in  his  tables  gives  the  following  figures  concerning  the  Nubian  vulture : Weight 
of  bird,  8152  grams ; surface  within  contour,  1. 11295  sq.  meters;  spread  of  wings,  2.66  meters; 
mean  width  of  wing,  .46  meters.  One  square  meter  sustains  7323  grams.  Relative  surface 
required  to  sustain  So  kilos.,  or  176.4  lbs.  avoirdupois,  lO.SS  sq.  meters,  or  117  sq.  feet,  16  sq. 
inches. 


MISCELLANY. 


213 


ular  to  the  chord  of  the  profile  curve,  but  that  in  certain  impact  angles  of 
the  air  its  direction  inclines  forward,  with  a perceptible  drawing  component.* 
— Liltenthal,  March,  i8gj. 


Lilienthal  wrote.  May  28,  1896 : “ I would  finally  remark  that  bodily 
strength  and  dexterity  are  of  less  consequence  than  the  general  intelligence 
and  the  gift  of  perception  in  technical  matters  when  selecting  the  men  [for 
gliding  experiments].” 


MISCELLANY. 

igio. 


THE  METHOD  WHICH  BROUGHT  SUCCESS. 


In  September,  1901,  Mr.  Wilbur  Wright  in  addressing  the 
Western  Society  of  Engineers  said:  “If  I take  this  piece  of 
paper,  and  after  placing  it  parallel  with  the  ground,  quickly  let 
it  fall,  it  will  not  settle  steadily  down  as  a staid,  sensible  piece 
of  paper  ought  to  do,  but  it  insists  upon  contravening  every 
recognized  rule  of  decorum,  turning  over  and  darting  hither  and 
thither  in  the  most  erratic  manner,  much  after  the  style  of  an 
untrained  horse.  Yet  this  is  the  style  of  steed  that  men  must 
learn  to  manage  before  flying  can  become  an  every  day  sport. 
The  bird  has  learned  this  art  of  equilibrium,  and  learned  it  so 
thoroughly  that  its  skill  is  not  apparent  to  our  sight.  We  only 
learn  to  appreciate  it  when  we  try  to  imitate  it.  Now,  there  are 
two  ways  of  learning  how  to  ride  a fractious  horse ; one  is  to 
get  on  him  and  learn  by  actual  practice  how  each  motion  and 
trick  may  best  be  met ; the  other  is  to  sit  on  a fence  and 
watch  the  beast  a while,  and  then  retire  to  the  house  and  at 
leisure  figure  out  the  best  way  of  overcoming  his  jumps  and 
kicks.  The  latter  system  is  the  safest,  but  the  former,  on  the 
whole,  turns  out  the  larger  proportion  of  good  riders.  It  is 
much  the  same  in  learning  to  ride  a flying-machine ; if  you  are 

'^Mit  nicht  unerkeblich  ziehender  Componente. 

For  Lilienthal’s  mathematical  treatment  of  this  subject  see  “ Zeitschrift  fiir  Luftschiffahrt,” 
February  and  March,  1S9C,  and  also  the  very  interesting  manual  entitled  “ Taschenbuch  f’ir 
Fluijtechniker  und  Luftschiffer,”  by  Captain  H.  W.  L.  Moedebeck,  published  by  W.  H.  Kiihl, 
Berlin,  1S95. 


214 


THE  AERONAUTICAL  ANNUAL. 


looking  for  perfect  safety,  you  will  do  well  to  sit  on  a fence 
and  watch  the  birds,  but  if  you  really  wish  to  learn,  you  must 
mount  a machine  and  become  acquainted  with  its  tricks  by 
actual  trial.”  (Smithsonian  Report,  1902,  p.  134.) 


MOTORLESS  FLIGHT. 


Experimenters  who  intend  to  devote  themselves  exclu- 
sively to  the  development  of  the  motorless  flying-machine  will 
be  interested  in  reading  the  following  authors : 

A.  M.  Wellington.  “The  Mechanics  of  Flight,”  Engineering  News, 
New  York,  Oct.  12,  1893. 

Wilbur  Wright.  Report  of  the  Smithsonian  Institution  for  the  year 
ending  June  30,  1902,  page  147. 

Wilbur  Wright.  “ Flying  as  a Sport,”  Scientific  American,  New  York, 
Feb.  29,  1908. 

L.  P.  Mouillard.  The  Aeronautical  Annual,  No.  3,  1897,  pages  158 
and  159. 

Octave  Chanute.  The  Aeronautical  Annual,  No.  2,  1896,  pages 
60-76.  The  Same,  No.  3,  1897,  pages  98-127. 

As  stated  on  other  pages,  the  Smithsonian  Reports  may  be 
found  in  the  principal  public  libraries  of  the  United  States,  and 
the  three  issues  of  “The  Aeronautical  Annual,”  1895,  1896, 
and  1897,  may  be  found  in  the  public  libraries  of  every  city  in 
the  United  States  having  a population  of  100,000  or  more. 
The  editor  is  uncertain  whether  the  “ Engineering  News  ” for 
1893  will  be  found  in  many  public  libraries.  Mr.  Wellington’s 
paper  was  also  printed  in.the  “ Proceedings  of  the  International 
Conference  on  Aerial  Navigation  held  in  Chicago  in  1893  ; ” 
published  in  1894  by  “The  American  Engineer  and  Railroad 
Journal,”  New  York.  This  book  contains  over  four  hundred 
pages  of  valuable  matter.  It  is  rare. 

It  is  very  unfortunate  that  so  much  of  the  literature  which 
would  be  valuable  to  the  students  of  aviation  is  out  of  print. 
Original  editions  were  usually  small,  but  they  were  larger  than 
was  necessary  to  meet  the  demand  at  the  time  of  publication. 


% 


MISCELLANY. 


/.,  215 


TWO  HUNDRED  PAGES  OF  READING  MAI  .U- 

ABLE  TO  THE  STUDENTS  OF  AVIATION. 


See  the  Annual  Reports  of  the  Smithsonian  Institution  for  the 
years  given  below.  These  may  be  found  in  the  principal  public  libra- 
ries of  the  United  States  and  in  many  European  libraries. 

Since  1897  the  Reports  have  borne  two  dates  upon  the  back  of 
binding.  The  lower  date  is  that  of  publication.  The  upper  date  is 
the  one  here  given. 

1892.  The  Empire  of  the  Air. 

By  L.  P.  Mouillard,  pp.  397-463. 

1897.  On  Soaring  Flight. 

By  E.  C.  Huffaker,  pp.  183-206. 

1900.  Lord  Rayleigh  on  Flight,  p.  195. 

1900.  The  Langley  Aerodrome,  pp.  197-216. 

1901.  The  Greatest  Flying  Creature. 

By  Langley  and  Lucas,  pp.  649-659. 

1902.  Some  Aeronautical  Experiments. 

By  Wilbur  Wright,  pp.  133-148. 

1903.  Aerial  Navigation. 

By  Octave  Chanute,  pp.  173-181. 

1904.  Experiments  with  the  Langley  Aerodrome. 

By  S.  P.  Langley,  pp.  1 13-125. 

1908.  The  Present  Status  of  Military  Aeronautics. 

By  Major  George  O.  Squier,  U.S.A.,  pp.  1 17-144. 

1908.  Aviation  in  France  in  1908. 

By  Pierre-Roger  Jourdain,  pp.  145-159. 


2i6 


THE  AERONAUTICAL  ANNUAL. 


MEMORABLE  EVENTS. 


FLIGHTS  WITH  MOTOR  AEROPLANES. 


Z>etr.  ly,  JQOj. 

Wilbur  Wright  in  North  Carolina  flew  852  feet.  This  was  the  first 
successful  flight  in  history. 


Nov.  g,  I go  4. 

Wilbur  Wright  near  Dayton,  Ohio,  flew  3 miles. 

Oct.  5,  igoy. 

Wilbur  Wright  near  Dayton,  Ohio,  flew  24  miles. 

Sept,  g,  jgo8. 

Orville  Wright  at  Fort  Myer,  Va.,  broke  three  world’s  records. 
In  the  morning  he  flew  57  minutes,  31  seconds,  breaking  the  record 
for  duration  of  flight.  In  the  afternoon  he  made  a flight  of  62  minutes, 
1 5 seconds,  thus  breaking  his  own  record.  A third  flight  was  made  with 
Lieutenant  Lahm  as  passenger.  Time  6 minutes,  10  seconds.  This 
surpassed  the  world’s  record  for  doubles. 

Sept.  21,  jgo8. 

Wilbur  Wright  at  Auvours  made  a record-breaking  flight  of  i hour, 
31  minutes,  20  seconds. 

Dec.  31,  igo8. 

Wilbur  Wright  at  Auvours  won  Michelin  prize  by  a flight  of  2 hours, 
20  minutes,  23  seconds. 

July  25,  igog. 

Louis  Bleriot  made  the  first  flight  across  the  English  Channel. 

July 30,  igog. 

Orville  Wright  made  cross-country  flight  of  ro  miles.  Fort  Myer, 
Va.,  to  Alexandria  and  return ; over  very  difficult  country. 


MISCELLANY. 


217 


Aug.  2j,  igog. 

Henri  Farman  at  Reims  flew  112  miles  in  3 hours,  4 minutes,  57 
seconds,  winning  first  prize  for  distance.  Hubert  Latham  at  Reims 
won  first  prize  for  altitude,  508  feet. 

Aug.  28,  igog. 

Glenn  H.  Curtiss  at  Reims  flew  20  kilometers  in  15  minutes,  50% 
seconds,  winning  the  Gordon-Bennett  International  Cup. 

Sepi.  8,  igog. 

S.  F.  Cody  in  England  made  cross-country  flight  of  40  miles. 

Sept.  18,  igog. 

Orville  Wright  at  Berlin,  with  Captain  Engle  hard  t as  passenger, 
made  flight  of  i hour,  35  minutes,  47  seconds. 

Oct.  4,  igog. 

Wilbur  and  Orville  Wright.  The  former  at  New  York  made  flight 
above  Hudson  River  to  Grant’s  tomb  and  return,  21  miles.  The  latter 
in  Berlin  reached  altitude  of  1600  feet. 

Oct.  18,  igog. 

Count  de  Lambert  made  flight  from  Juvisy  to  Eiffel  Tower  and  return, 
31  miles. 

Nov.  3,  igog. 

Henri  Farman  at  Mourmelon  flew  4 hours,  17  minutes,  53  seconds, 
breaking  world’s  records  for  duration  and  distance. 

Dec.  I,  igog. 

Hubert  Latham  at  Mourmelon  rose  1500  feet. 

Jan.  12,  igio. 

Louis  Paulhan  at  Los  Angeles  reached  altitude  of  4165  feet,  sur- 
passing world’s  record. 

April  23,  igio. 

Claude  Grahame-White  flew  from  London  to  a point  near  Lich- 
field, 1 13  miles.  Left  Wormwood  Scrubs  at  5.15  a.m.,  Arr.  Clifton, 
near  Rugby,  7.20  a.m.;  Left  Clifton,  8.25  a.m.,  Arr.  Hademore  Cross- 
ing, 9.20  A.M. 

April  27  and  28,  igio. 

Louis  Paulhan  flew  from  London  to  Manchester,  186  miles,  winning 
Daily  Mail  Prize  of  ^50,000. 

Left  London,  5.20  p.m.,  Arr.  Lichfield,  8.10  P.M.,  April  27 ; Left  Lichfield, 
4.09  A.M.,  Arr.  Manchester,  5.30  a.m.,  April  28.  Total  time  of  flight,  4 
hours,  II  minutes. 


EDITORIAL 

1910. 


THE  FUTURE  OF  AVIATION. 


In  comparing  the  Stockton  and  Darlington  railway  and  its 
equipment  with  the  transcontinental  roads  and  trains  of  torday, 
or  in  comparing  Fulton’s  “Clermont”  with  the  “Mauretania,” 
we  see  what  may  be  evolved  from  crude  prototypes. 

If,  in  the  early  years  of  the  last  century,  there  were  men  who 
predicted  the  developments  in  transit  which  were  destined  to 
come,  they  were  undoubtedly  deemed  visionary.  As  a matter 
of  fact,  they  were  so,  but  their  dreams  have  come  true. 

It  is  probable  that  the  forecasts  of  those  sanguine  ones  were 
lightly  regarded  and  perhaps  they  were  told,  “ You  cannot  see 
the  limitations  of  these  locomotives  and  steamboats ; you  do 
not  in  the  least  know  whether  the  obstacles  which  will  be  met 
in  trying  to  adapt  them  to  the  larger  uses  of  mankind  will  be 
surmountable  or  not.”  That  would  have  been  just  criticism 
and  it  may  illustrate  the  position  in  which  men  stand  to-day  in 
relation  to  the  problems  of  aerial  travel. 

Aviation  as  a sport  is  here  and  it  is  here  to  stay.  Military 
experts  seem  to  be  agreed  that  in  the  unfortunate  event  of  war 
the  dynamic  flying-machine  in  its  present  state  of  development 
will  be  of  great  importance  for  scouting  purposes.  These 
experts  are  far  from  being  in  agreement  concerning  the  utility 
of  the  flying-machine  for  offensive  purposes  in  warfare. 

Leaving  aside  the  adaptability  of  the  flying-machine  to 
military  and  sporting  purposes  and  considering  its  strictly  utili- 
tarian value  in  time  of  peace,  it  may  be  said  that  those  who 
have  given  the  most  study  to  the  subject  of  aviation  seem  to 

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EDITORIAL. 


219 


agree  in  thinking  that  at  no  distant  day  a useful  machine  will 
be  developed.  As  to  the  possible  extent  of  the  useful  service 
which  it  may  render  in  the  future,  we  are  in  a state  of  ignorance. 
There  are  conservatives  and  there  are  visionaries.  Looking 
backward  a few  centuries  to  the  time  when  man  began  to 
conquer  distance  and  looking  at  his  present  powers,  we  see  that 
the  visionaries  have  come  out  ahead. 

The  great  utilitarian  task  which  is  now  before  us  is  to  navi- 
gate the  air  through  darkness,  fog,  and  storm.  Can  the  obstacles 
be  overcome? 

Looking  down  a few  hundred  feet  from  the  summit  of  a low 
mountain  opposite  the  entrance  to  one  of  the  very  long  Alpine 
tunnels,  the  sinuous,  glittering  line  of  rails  may  be  seen ; it 
vanishes  in  a black  pin-hole  at  the  steep  base  of  a mountain 
of  rock  thousands  of  feet  high.  In  the  earlier  time  what  a 
dead  wall  was  that ! How  would  it  have  appeared  to  George 
Stephenson? 

Now  a train  comes  along,  it  disappears,  it  will  emerge  miles 
away. 

However  it  may  be  with  individuals,  mankind  itself  is 
undaunted  in  the  face  of  obstacles. 


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FROM  THE  INTRODUCTION  TO 
THE  AERONAUTICAL  ANNUAL,  NO.  1,  1895. 

IF  this  compilation  should  happily  bring  any  new  'workers  into  the 
field  of  aeronautical  experiment,  the  hopes  of  the  editor  -will  be 
amply  fulfilled. 


EXTRACT  FRC  >1  A LETTER  TO  THE  EDITOR 
DATED  DAYTON,  OHIO,  JANY.  15TH,  1908. 

The  Ola  Annuals  were  largely  responsible  for  the  active  Interest  which 
led  us  to  begin  experiment  In  aeronautics. 

Very  truly  yours. 


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